JOHN LOCKE
(1632-1704) was an English doctor and philosopher who was very
influential on the American Founding Fathers (Hamilton, Madison,
Jefferson), the Declaration of Independence and Constitution. Thomas
Jefferson considered him one of the greatest thinker who ever lived.
One
passage of the Declaration of Independence is almost wholesale lifted
from Locke’s political work. He was friends with scientists such as
Boyle and Newton. He is famous for two works, the classic text of
Empiricism, An Essay Concerning Human Understanding, and the political
text, Two Treatises of Government.
We
cover Locke’s political thought more extensively in the Social and
Political Philosophy class, but a short summary is appropriate here.
Locke believed that the power of the king must not infringe on the
right to life, the right to liberty, and the right to property, and this
must be achieved by establishing a separation of powers and a system of
checks and balances. Locke argues that the people have the right to
rebel against the sovereign if the sovereign infringes on these rights.
As
many critics have pointed out, neither Locke nor the American founding
fathers believed that these rights extended to all of humanity and there
resulted great contradictions between love of individual rights and the
brutal practices of slavery and colonialism. Locke was a major
investor in the Royal African Company, a secretary to the Council of
Trade and Plantations and a member of the Board of Trade, all of which
were central to the African slave trade that took Africans from West
Africa to the Americas to benefit English plantations. While he argued
that labor gives the individual a natural right to property, he also
argued that the work of servants and slaves rightfully belongs to their
master. Like the founding fathers wrote “All men are created equal” but
owned slaves themselves, Locke was clearly in agreement with the racism
of his times and was writing for the equality of Europeans who owned
property, servants and slaves and not of all-inclusive humanity.
An
Essay Concerning Human Understanding is Locke’s famous work on
epistemology, the study of how we learn and understand things. For many
who lean towards skepticism, like myself, epistemology and ontology
(the study of what exists) are one and the same, as our understanding is
our reality. On a winter afternoon in 1670, Locke met with friends to
have a discussion about morality, ethics and religion, but the group
could not come to much agreement on any subject. This made Locke wonder
about how we come to understand things. He sat down later to write
what he thought would be a single page on the subject, and instead spent
much time for over twenty years writing his central philosophical work,
publishing it in 1690. The text significantly influenced Hume, who we
will consider next, and Berkeley, who we will examine next time, both
largely in agreement with Locke’s conclusions. Leibniz, who we last
covered, wrote a Rationalist rebuttal to the text, addressing Locke’s
work point by point.
In
the beginning of the text, Locke compares our faculty of understanding
to the eye, an object that is invisible to us and difficult to put at a
distance from which we can examine it properly. The word ‘faculty’ is
used by philosophers to refer to parts of the mind, similar to organs of
the body, but in the brain, itself a single organ. Locke has us
consider the newborn baby, which gives us little reason to think there
are innate ideas or understandings. While Locke supposes that in later
stages of prenatal development the fetus can have experiences, he
stresses that it is through experience, being impressed by perceptions,
that the child comes to have understandings. Locke is attempting to
refute Rationalism and the position of Descartes. Locke argues that
young children and the insane do not hold mathematics or identity to be
true, but must learn these things. It appears Locke is considering a
child play acting, pretending to be a caped hero. Children like sweet
things, but they have no idea what sweetness is until they taste it.
Thus, while human anatomy may be predisposed to sweet tastes, the idea
of sweetness must be acquired through experience.
To
bring in an example from outside the text, we know that when animals
and humans watch each other perform actions, their own brain lights up
as if they themselves are performing the action with their own body and
nervous system, but that this is repressed in a way such that the
watcher does not mistakenly believe themselves to have acted.
Psychologists have observed that, after only two months of age, babies
can follow the direction of others’ eyes, follow the gaze to see what
the other is observing, and if they do not see anything significant they
double check and try again. It is not that the baby has an innate idea
that they, like the one they observe, is a human being as opposed to a
rock, but rather that the baby finds such things highly stimulating and
only later comes to have conceptions of humanity and individual
identity.
Locke
famously argues that the individual mind is originally a blank slate, a
‘tabula rasa’, ‘blank slate’ in Latin. In the early days of human
writing, scribes would write by making impressions on a clay tablet. As
an Empiricist, Locke believed that there are no innate ideas in the
human mind and that all ideas are acquired by experience, much like his
fellow Empiricist Hume. Locke had before this read a 12th century
Arabic novel (translated into Latin) by Ibn Tufail entitled Living Son
of Wakening which tells the story of a child isolated from human society
on a desert island who grows naturally by experience and reason to
human adulthood. Another popular novel at the time was Robinson Crusoe,
which features a civilized gentleman and native ‘savage’ on an island
in the state of nature. Locke believed that education is central to all
development and that the mind is an empty cabinet waiting to be filled,
a white piece of paper waiting to be written upon, a dark room waiting
to be filled with light.
If
we are each a blank slate, what constitutes our identity, our sense of
self? Locke argued that the self is a continuity of consciousness, an
extension of Descartes’, “I think, therefore I am”. Recall that
Avicenna and Descartes each argued that our consciousness is the one
thing about which we cannot be deceived. Locke takes the idea further
by considering consciousness as a continuous experience. Descartes had
focused on the moment that consciousness arrives at its own certainty
through rationality. While Descartes argued that from this fact we can
rationally deduce several other truths, Locke argued that we cannot by
reason alone deduce facts from consciousness, but only gather them
through its continuous experience.
In
my undergrad days as a philosophy major, we were given a thought
experiment to illustrate Locke’s idea of identity as continuity of
consciousness similar in ways to the “brain in a vat” used to illustrate
Descartes’, “I think, therefore I am”. Again, it involves a machine
that has the power to affect brains in ways as yet undiscovered.
Imagine two people are placed in a machine that switches the brains
between the two bodies and then similarly exchanges the contents of the
two minds. Let us assume that this is possible, and that the content of
the mind is much like software. Is person A now person B?
Locke
would argue that person A may be an entirely different person after the
process, but person A remains A and is not person B because B still has
their continuity of consciousness, and thus their individual identity,
even if that identity has been entirely altered. If someone has a case
of amnesia and cannot remember their name or anything about their life,
we would say that they are the same individual, identical with their
earlier self, but without their faculty of memory. At the time, I
disagreed with Locke, but now I think there are two sides to the
situation. On the one hand, we do consider the identity of a person to
be a function of quality, and so we say that someone who has severe
alzheimer's disease or catatonic schizophrenia to, “no longer be the
person we once knew”, as the expression goes. On the other hand, we
also consider identity to be a designator of quantity, and so like Locke
we would say that experiment subject A is not B in spite of the
transference of mental content. Note that if we were to somehow
transfer the consciousness of B along with the mental content, which the
imaginary machine does not have the power to do, Locke would have to
conclude that A is now B, as B’s mind is inhabiting the body of A.
Interestingly, if we switched first the brains and THEN the mental
content, Locke would have to conclude that A is now B, having the
consciousness of B, in spite of the fact that A retains A’s body and A’s
mental content.
Like
Descartes, Locke argues that it is rational to believe in mathematics,
discoveries of science, and God, but unlike Descartes, Locke argued that
these things are known through experience and evidence. While
Descartes argues that we can create rational arguments that prove the
existence of God, Locke argued that belief in God is rational based on
the evidence of miracles. Locke’s friend Newton believed the same,
arguing that the solar system would spin out eventually if it were not
for the fact that God poked his finger in occasionally to straighten it.
Locke argues that it is rational to suppose that there is an
omnipotent, omniscient being, but that it does not matter whether we
please to call it ‘God’ or not. This is quite deist, similar to the
thinking of Locke’s admirer Jefferson as well as the thinking of
Spinoza. Also like his friend Newton, Locke believed that animal
spirits, electric in nature, reside in the muscles and communicate with
the brain.
While
Locke does admit the existence of rational reflection, this is always
reflection upon experience or upon ideas acquired from experience.
Hume, we will soon see, expands on this. From initial ideas derived
from sensation, such as solidity and motion, we then construct
additional ideas. Consider that our idea of truth is based very much on
our experience of solidity. In older English, if something “holds
true”, this can be either mental or physical. If an argument or
understanding is “solid”, we can use it as a “base” to “support” other
ideas, holding them up such that they are solid like the basis on which
they are founded.
Locke
makes a distinction between simple ideas such as colors, shapes,
tastes, and complex ideas such as identity and cause and effect. Hume
follows Locke in arguing that cause and effect is a complex idea, a
concept composed of several elements that we put together mentally.
Locke also makes a distinction between primary qualities, such as
shape, arrangement and motion, and secondary qualities, such as color
and taste. Primary qualities are objective, whereas secondary qualities
are subjective sensations that do not objectively exist but only via
subjective experience. Consider the example of a red square. Locke
would say that the square is objectively shaped the way that it is, but
red is a color that only some can see, unlike a dog who is colorblind.
Note the similarity to Descartes, who argued that some things that seem
certain can be assumed to be certain, in spite of the fact that we can
doubt all our experiences.
Many
have questioned this second distinction, asking if there is an
exclusive divide between objective and subjective qualities. It does
seem that the shape of a square is not open for debate, much like two
and three equaling five. However, we can conceive, like Descartes, that
this is an individual or even collective illusion. Locke does say that
we can imagine that our senses were different in number, and that this
would profoundly affect our experience of the world. What if our
tactile and visual senses were greatly enhanced, such that only near
perfect squares appeared square to us? What if we gained senses that
gave us experiences unlike any we had before? While Locke considers
motion to be objective, like his friend Newton, Einstein argued that
motion is relative. We do not even need to approach light speed to
demonstrate this, as the Earth to us is stationary, and the stars make
circles overhead. The ancient Greek Pyrrhonian skeptic Sextus Empiricus
argued that shape and motion can vary by perspective. A cone appears
triangular from the side, yet circular from above. When we are in a
vehicle such as a chariot, everything that is standing still appears to
move. When we look at a ship far out to sea, it appears to stand still
but is moving quickly.
Locke
disagreed with Descartes that knowledge is clear and distinct.
Knowledge is only probable, and involves a complex coherence of ideas.
Oddly, this means that even as Locke considers primary qualities to be
objective and distinct from subjective secondary qualities, we can only
imperfectly know what is objective and primary. Locke arguing for a
noncontradictory coherence of ideas is similar to Leibniz, who believed
in the principle of noncontradiction. Locke argued that we can afford
to be certain when there is strong evidence, but should provisionally
entertain things when there is only weak evidence. New evidence must be
continuously sought, but coherent knowledge that is strongly supported
by evidence can be acquired. Locke uses his friend Newton and his
discovery of gravity as a positive example, as well as Jesus and his
ethical teaching to love one’s neighbor as one loves oneself. Note that
Locke considers Ethics to be a science, and considers both religion and
science to be rational pursuits. Locke attacks those who use
complicated terms and are obscure, very much the charge against the
Continental tradition by the Analytic tradition and the common language
movement.
DAVID HUME
(1711-1776) was born in Edinburgh, Scotland. His name was originally
‘Home’, but Hume changed it because his English colleagues kept
mispronouncing it. Like Descartes, he originally planned to study law
but came to a fascination with philosophy and devoted himself to it
instead. During his lifetime his works on philosophy were condemned
both by professors as unintelligible and priests as heretically atheist,
but his six volume History of England gained fame and was printed
numerous times. While Hume was called an atheist by friends and foes,
he was critical of religion but silent about his own beliefs. It is
likely he was an agnostic, as he argued in various places that reason
could neither prove nor disprove the religious beliefs of the world’s
cultures. Like Nietzsche, whom Hume influenced with his idea that
desire is always involved with reason and the two could not and should
not be considered apart from one another, Hume saw religion not as
objectively true or false but as useful to a culture in a time and
place, and in his History of England he argues that humans are creatures
of habit who are often only moved to political revolution over matters
of religion. Over the course of English history, religion was often the
only power other than the nobility that could put the monarchy in
check.
Hume’s
radically skeptical position, the one that awoke Kant, who we will
examine next time, from his “dogmatic slumbers”, is that all of our
thinking, our identity and truth is induction and assumption. This is
like the Indian theory of skandas, ‘piles’ of sand, viewing the mind and
all perceptions as bundles that accumulate and then dissipate.
Buddhists often use this to illustrate the doctrine of impermanence,
that all things are mortal and temporary. Also like Indian thought,
particularly Buddism, Hume argued that human thought, identity and
behavior are ruled by the passions, not reason which serves as a tool
for our desires. With Locke and Berkeley, Hume is one of the three
great British Empiricists. We shall be covering Berkeley next week with
Kant as an Idealist, as Berkeley does believe as an Empiricist that we
know nothing apart from experience, but he also believes, as an
Idealist, that the world is not material but in our minds.
Hume’s
text An Abstract of A Treatise of Human Nature is the condensed form of
Hume’s first and foremost work which he wrote after critics claimed his
original Treatise of Human Nature was convoluted and difficult to
understand. Hume starts saying that philosophy has flowered all over
Europe in “these last four score years” (80 years, no connection to
Lincoln or Gettysburg), and that it has occurred in England just as
greatly as any other. Notice that philosophy for Hume is a recent
development for Europe as well as England. Hume says that philosophers
of ancient times have handled their truths delicately, showing more
restraint than full depth of reflection. Remember that with Descartes,
skepticism and critical reflection can quickly turn to dogmatism and
orthodoxy. Hume argues that all truth is assumption, habit, and
prejudice, which means that any accepted truth must be continuously
justified rather than simply proved once with reason. This opens up the
potential for continuous attacks on all established forms of truth.
Hume
says that all mental activities are perceptions. Perceptions are
divided into two kinds: impressions and ideas. Impressions are
perceptions of objects that are present, and ideas are perceptions of
objects that are not present or not directly perceived. For example,
one has the perception of a red billiard ball on the table. Hume used
billiards, a leisure activity for aristocrats such as himself, to
illustrate his criticism of our conceptions of causation. If one turns
around and doesn’t look at the ball, one has an idea of the ball that
includes its appearance in one’s head. Our experience of the ball left
an impression on us which we can then recreate as an idea in our heads,
creating a new type of perception derived from our earlier direct
perception. Likewise, if one looks at the red ball and imagines it is
moving, one has an impression of the ball and has an idea of the ball
rolling down the table, supplementing a direct perception with an
indirect perception acquired from previous experience with billiard
balls. Likewise, if one looks at a moving red ball and imagines it is
going to continue moving or hit another ball, one has many impressions
of the ball as it moves that one gathers together with an idea of its
continued future movement.
Impressions
are strong and direct, while ideas are weaker and indirect. Hume
argues that we derive all of our ideas from our impressions. Hume
acknowledges that this is in line with Locke’s idea of tabula rasa, that
we are a blank slate upon which experience impresses its forms. This
goes directly against Descartes and Kant, who believe we can with the
operation of reason, independent of experience, determine several truths
that are correctly understood to be certain apart from our experience.
Just as Berkeley is an Empiricist, but also an Idealist, Kant is often
considered a Rationalist, like Descartes, Spinoza and Leibniz. Clearly,
even as early modern European philosophy picked up steam and moved into
the abstractions of Idealism, the rift between the dogmatic
Rationalists and skeptical Empiricists remained. As mentioned, this
leads to Hegel, who tried to take both sides and synthesize them.
Hume
presents us with his famous and central billiard ball analogy. Imagine
two billiard balls, one red and one blue, and that the red ball rolls
down the table, strikes the blue ball, and causes it to move. There are
three events here. First, the red ball moves up to the blue ball.
Second, there is the sound of a ‘clack’ as the two presumably collide.
Third, the blue ball moves away from the red ball. Naturally, and this
is the key word here as we are talking about a habit we naturally
acquire, we all arrive at the understanding that the red ball struck the
blue ball, causing it to move. We naturally assume that the motion of
ball A caused the motion of ball B.
Notice
that we did not see or perceive the conjunction of the two events. We
did not perceive the causation directly. While we saw two billiard
balls, saw two colors, saw to motions, and heard a ‘clack’, none of
these things characterize causation. Causation is itself invisible. It
has no color, does not always involve motion nor does it always make a
sound. Hume asks: How did we all understand ball A caused ball B to
move? Since we are a blank slate, as Locke argued and Hume supports,
how did we come to have the impression that A caused B to move? If
causation involves various sets of sensations without a common factor,
how can any particular impression lead to our idea? If Hume was a
Rationalist, he could claim that we reason that A caused B to move, but
as an Empiricist, who like Locke argues that our ideas can always be
wrong and experience can always present us with counterexamples, he
makes a much more radical and skeptical claim.
The
answer, Hume says, is that we all have shared common experience, and so
we share ideas and prejudices. Since we were infants, we have all seen
solid things move into other solid things, followed by further
movements. While various sensations such as sights and sounds were
involved, we each developed a similar idea of causation that we derived
not from abstract reason but from direct experiences. We developed a
habit and prejudice such that when we watched the red ball moving toward
the blue ball, we assumed that the blue ball would move, and then when
our impression of the blue ball moving matched our idea, we assumed that
our prediction was accurate and further reinforced our idea.
Note
that assumptions lead to and reinforce further assumptions, not
certainties of reason leading to further certainties, as the
Rationalists would have it. Our impressions of things knocking into
each other, and in particular our impressions of billiard balls and
their motions, naturally caused us all to have a preconception, a
preconceived idea, that the red ball was going to hit the blue ball and
then the blue ball was going to move afterward. Then, when things
happened as they usually seem to, we all come to the conclusion,
individually and as a group together, that we were right in our
preconceptions.
Hume
believes that this is all one can strictly say about the events, and
that saying anything else, like suspecting that a particular ‘causation’
was there as an invisible presence that we can know with certainty, may
be a common idea but it is in fact not directly perceived or known.
Most often, our conclusions are correct, but whenever they are wrong,
it shows us that we can assume things are certain through preconceived
ideas, but these do not guarantee that we will be correct. Feyerabend,
my favorite skeptical philosopher of science, says that circular reason
is not necessarily a fallacy, as it is the most dominant form of
reasoning on the planet and much of the time it is perfectly correct.
Consider
that we could make a movie of the two billiard balls, filming ball A
striking ball B, and then display the film to an audience. While every
member of the audience would assume that ball A caused ball B to move,
they are all watching an image, not the physical act, and so the image
of ball A is not causing the image of ball B to move. It is the media
of the film, today digital data, that causes the image of ball B to
appear and move. It is an illusion that one image is striking the
other. Obviously, we want the audience of the film to have this idea,
but this does not make it any less of an illusion, whether the billiard
balls are filmed or animated. In a sense, when we watch animation we
know and don’t know that what is going on is ‘real’. We can ‘suspend’
our disbelief, and allow our minds to watch and believe in the animated
events, even though any animation must, by its nature, be false
caricatures of events.
It
is very similar to the Belgian Surrealist painter Magritte’s painting,
“This is not a Pipe”, displaying the image of a pipe. In the same way,
we can gaze at a painting of a pipe, know very well that this pipe
cannot be smoked, yet suspend our disbelief to accept the image as a
representation that the painter is conveying to us. Magritte’s painting
is an attempt to invert this situation, an image that draws attention
to being a mere representation rather than allow the spectator to ignore
the fact. Likewise, we can construct an animatronic billiard table,
like at a ride in Disneyland, that looks like objects are hitting each
other over and over again even if the sound is artificial and the
objects never touch. Roland Barthes, the French philosopher and
literary critic, said that now that we have built Disneyland, maybe we
will be more critical of our perceptions of society.
Hume
argues that all of our beliefs and truths are inferences that we draw,
not certainties that we can know without qualification. This is true of
life, history, and all of philosophy. If this seems hopeless in its
skepticism, it is not entirely bad. Remember that most of our
preconceptions are quite in accord with how things go, otherwise we
would have no reason for forming them in the first place. While nothing
can be known for certain, our impressions do accumulate and build up in
our ideas, and thus they are real and useful to us. They are not so
real that they ensure that nothing could ever contradict them, but they
are real to us and we often use them successfully in the world. Hume
uses the example of Adam in the garden of Eden as a human who learns by
experience, starting with a blank slate. Hume writes:
“Even
Adam, with all his science, would never have been able to demonstrate
that the course of nature must continue uniformly the same, and that the
future must be conformable to the past.”
“We
are determined by custom alone to suppose the future conformable to the
past. When I see a billiard ball moving towards another, my mind is
immediately carried by habit to the usual effect, and anticipates my
sight by conceiving the second ball in motion…It is not, therefore,
reason which is the guide of life, but custom. That alone determines
the mind, in all instances, to suppose the future conformable to the
past. However easy this step may seem, reason would never, to all
eternity, be able to make it.”
“With
regard to any matter of fact, however strong the proof may be from
experience, I can always conceive the contrary, though I cannot always
believe it…Philosophy would render us entirely Pyrrhonian were not
nature too strong for it”.
Hume
argues that things are often variable and uncertain in life. Using a
modern example, very similar to examples used by Sextus Empiricus to
support Pyrrhonian skepticism, Hume argues that thirty grains of opium
will kill anyone that is not accustomed to it. Clearly, Hume is
accustomed to people using opium. Hume questions the Cartesians’ idea
of a supreme being which is wholly without deception, the eternal soul,
and the absolute certainty of mathematical truths such as 2 + 3 = 5. He
argues that the Cartesians cannot know these things from experience,
and they cannot derive them from reason.
Hume
argued that the idea of God is a composition of our experience that we
have not experienced directly so much as in other things. Human beings
saw men with beards rule over things on high, and they project from
their experiences in the world into realms unseen. Recall that Locke,
like many deists such as Spinoza, did not believe in an anthropomorphic
god, and would agree with Hume’s bold statement, the sort that had him
labeled a heretic even as he kept his true beliefs secret and kept the
secret to the grave.
Mathematical
and geometric proofs look nice, but sometimes geometry seems like it is
proving something that is later disproved, as Descartes himself notes
as he imagines a demon that could deceive him even about forms of
mathematics. While Hume and other Empiricists would freely admit that
it is very useful to follow one’s assumption that 2 + 3 = 5, this is
based on our experience of the durability of this truth in the world,
not based on purely abstract reasoning.
As
mentioned Hume argued that emotion and reason are always intertwined,
just as experience and reason are always intertwined. He famously said,
“Reason is, and ought only to be the slave of the passions”. Without
desire, we do not reason. Recent literature about antidepressants
suggests that when people are significantly devoid of desire, they do
not find themselves thinking much, are not motivated to have significant
ideas about important things. When we think much about something, we
are passionate.
I
gave you selections from Hume’s other important work, An Enquiry
Concerning Human Understanding. Hume says that much philosophy has been
concerned with proving the existence of God, as we have seen so far in
the philosophers we have covered. While much effort is made to refute
atheism and skepticism, it is also asserted that complete atheism or
skepticism are impossible. Hume wonders how a knight could continuously
wander the countryside, seeking to defeat dragons and giants, while
convinced that they do not exist. I must say as a skeptic myself, quite
opposed to much of Analytic thought, I have found it continuously
amusing to hear again and again that skepticism is a problem that must
be overcome, in spite of the fact that there are very few hard skeptics
in the Analytic tradition and much thought is done while skepticism
remains, apparently, as yet undefeated. Sextus, the Pyrrhonian, argued
that dogmatists, by arguing against skepticism (as well as each other)
betray their own position, giving us good evidence that their dogmas can
be doubted and opposed.
Hume
criticises Descartes and the Rationalists who seek an absolute and
unquestionable starting point from which to reason. Such a point does
not exist, as all truth can be doubted, as ancient Pyrrhonian skepticism
recommended. If each and every sensation can be doubted, then so can
each and every act of reasoning. While the Pyrrhonians doubted
sensations with good examples such as an oar appearing bent in water,
Hume is concerned that Descartes can doubt sensation as well as any
Pyrrhonian but cannot doubt reason, in fact attempts to defeat
Pyrrhonian skepticism through the use of reason. It seems that reason
is more difficult to doubt than sensation. For Hume, this is
disturbing, given that all of our reasoning and ideas are derived from
and dependent on sensation. I previously mentioned that Nietzsche was
quite critical of philosophers such as Plato and Descartes for
considering ideas to be more certain than physical things, and Nietzsche
was quite fond of Hume and skepticism.
Hume
argues that the great subverter of skepticism is employment, the
occupations of common life. Because we must act and eat, we cannot
afford to be entirely skeptical. While it is easier to be skeptical in a
school or in the shade, as soon as we are passionate about things in
the world skepticism, even for the hardened and determined skeptic,
vanishes like smoke. The only genuine profession for the skeptic is
philosophy. If the entire world were made of nothing but skeptical
philosophers, humanity would die out, but thankfully we are naturally
ignorant, passionate, and dogmatic, and so skepticism is continuously
useful for showing most people the continuous errors of their ways and
that for every position there is a counter position even if it does not
seem apparent at first. Thus, while skepticism, philosophy and doubt
would be worthless if they eclipsed all dogmatism, vocation and belief,
they are the most useful of positions and vocations, in critical
opposition to everything else on Earth.
