Hume nearly killed metaphysics. Immanuel Kant saved it, but at a
cost. In resuscitating metaphysics, Kant attempted to mend a great
philosophical divide, and in doing so he created the boundaries which
he believed would change the very nature of metaphysics.
For hoi polloi, metaphysics is philosophy—most picture tweed-jacketed
men sitting in patent leather wing-back chairs smoking pipes and
pontificating on the ultimate nature of reality. Yet for the
philosopher, the term metaphysics refers to a specific study within philosophy, namely the study of
problems and concepts with are beyond or
transcend the physical
while questions relating to the properties of iron alloys, or the
growth and reproduction of Conium maculatum,
are clearly grounded in the physical world of the natural sciences; questions about the existence of
things outside of our consciousness, or the ultimate reasons for the
existence of the universe, say many philosophers, cannot be answered
by appealing to the physical world: instead one must look beyond, to metaphysics.
had long been the bread-and-butter of many philosophers, but the
middle of the 18th century brought a strong challenge: a Scottish philosopher and
historian named David Hume.
Hume stood on one side of a very important philosophical divide that
existed in both the 17th and 18th centuries. Hume, along with other philosophers like John Locke and
George Berkeley, represented the empiricist camp.
These philosophers tended to discount the importance of innate
reasoning and logic in gaining knowledge, instead arguing that the
way to discover valid knowledge was through experience and
Kant, a decade Hume's junior, started his career in philosophy
occupying an opposing camp. Kant, following a tradition defined by
many continental figures, chief among them Descartes and Leibniz,
began as a rationalist—he
felt that the way to valid human knowledge was not through
experience, but instead through pure intellectual processes such as
Kant's rationalism was not to last: famously (at least among
philosophy students) Kant wrote, “I
openly confess that my remembering David Hume was the very thing
which many years ago first interrupted my dogmatic slumber and gave
my investigations in the field of speculative philosophy a quite new
awaking lead him to write his massive and Byzantine Critique
of Pure Reason and its
follow-up, Prolegomena to Any Future Metaphysics.
Both of these examine the role and possibility of metaphysics, but
our focus shall be Kant's simpler Prolegomena.
his preface to the Prolegomena, Kant
asks, “Whether such a thing as metaphysics be at all possible?”
His answer, through the rest of the Prolegomena is, in essence, Metaphysics is possible, but not as it has been done in the past. There are boundaries, he
argues, to what the study of metaphysics can uncover, but Kant
ultimately concludes that with a new, critical approach the study of
metaphysics is possible and can be rescued from some of Hume's
Kant asks, “How is pure mathematics possible?” Mathematics,
argues Kant, is the product of “pure reason.” More accurately,
Kant categorizes pure mathematics as involving both a
priori reasoning and synthetic
All forms of
knowledge and reasoning, for both Kant and most other philosophers,
can be divided into two forms: a priori and a posteriori. The vast
majority of our knowledge—from the name of Paris Hilton's latest
movie, to the number of electrons in a silver atom—can be
classified as a posteriori knowledge.
We know the name of Paris Hilton's movie because we've seen it, or
read a review about it. We know the number of elections in a silver
atom because we've consulted either a periodic table or Google. A
posteriori knowledge is derived
from our experiences, specifically from our experiences of sensory
data regarding the world around us; in other words, I know the sky is
blue because I can see that the sky is blue.
priori knowledge, on the other
hand, arises from our reasoning, logical faculties: it has nothing to
do with our sensory data and personal experiences. Tautologies like
“A is A” can be said to be true, no matter what experiences we've
encountered—in fact one could claim that even a logical individual
with no personal experiences whatsoever could know that the claim “A
is A” is true. A priori knowledge
obviously represents a much smaller amount of our overall knowledge.
also distinguishes between two different ways of gaining knowledge.
One way we can gain knowledge, according to Kant, is through analytic
judgments. These analytic
to clarify knowledge we already have: they do not add any new data,
they merely 'unpack' or extend the data already contained within a
statement or piece of knowledge. To use a well-worn example, take the
claim “all bachelors are unmarried,” this claim is, according to
Kant's categorization, an analytic
judgment because the claim about the martial status of bachelors in contained
within the concept of the word 'bachelor'. In other words, this claim
merely 'unpacks' the word bachelor into a sentence.
claim “all bachelors eat poorly,” would be an example of a synthetic judgment.
While it may be true that all bachelors eat poorly, the dietary
status of all bachelors is not contained in the concept of 'the
bachelor'. Instead this information is added; Kant claims that synthetic
judgments add information from one of three channels. There are judgments
which naturally utilize a
in creating a claim. Mathematical
judgments utilize a priori information
about mathematical laws—Kant makes it clear that while mathematics
may appear at first to fall under analytic
because the results of mathematical operations come from intuitive
syntheses and not from the numbers themselves, mathematical
operations fall under synthetic
Kant argues there are metaphysical
are based on a
and answer questions outside of the realm of mathematics.
can now return to Kant's question “How is pure mathematics
possible?” Kant argues that pure mathematics, which, as stated
above, consists of a
priori, synthetic judgments, is
possible because of pure
occurs when we come to a conclusion or belief about something without
any logical, reasoning process to guide us there.
you meet an occasional acquaintance at a bus-stop. Immediately you
think to yourself, This
is Fred, the skinny, blond bachelor from work. The
knowledge you have about Fred falls into two categories. The first
represents our normal knowledge: you know he is named Fred because he
introduced himself as such, and you know he is bachelor because Laura
from accounting told you so. These pieces of knowledge come to you
through discernible channels (Fred himself, or Laura from accounting)
and you apply them consciously (at least theoretically consciously)
to Fred as the subject.
knowledge that Fred is both skinny and blond is different though: it
represents gained through empirical
or intuition about what we perceive. Once you've met Fred and seen
has to tell you that he is blond, you just know, without any explicit
reasoning or evidence. You never needed to learn about the qualities
of the concept of 'skinniness' in order to apply the term to Fred, he
simply is skinny.
says that we have another type of intuition in addition to our empirical
we also possess what Kant refers to as pure
intuition. Our pure intuition,
says Kant, exists in the form
something like a 'filter' which proceeds our empirical perceptions,
allowing us to interpret the data we receive from our senses.
Naturally, because it proceeds our perceptions, this pure
the form of
is a priori:
we do not need any experience to have knowledge of it.
This pure intuition comes
in two very specific forms: 'time' and 'space'. Thus, argues Kant,
time and space are not things-in-themselves,
or in Kantian terms, noumena. Instead
they are filters through which we perceive and order the phenomena, in
other words, the world as it appears to us through our senses. And
vitally, claims Kant, we know both the concepts of time and space a priori.
argues Kant, relies on the application of our pure intuition
regarding time and space. Because of this, pure mathematics is
possible, as it stands on firm, a
Next Kant turns
his attention to the question, “How is pure natural science
possible?” In more modern terms, Kant is asking how our knowledge
regarding the physical, tangible world is 'possible'.
potential problem Kant sees in the natural sciences, and more
broadly, with our knowledge of the physical world arises because of
how we perceive the world around us. According to Kant, there exists noumena,
are objects which exist separate from us. Yet Kant argues that the noumena are distinct from what he refers to as the phenomena,
or our perception of these noumena.
simple terms, when I perceive an object, for example a bachelor, I do
not have direct access to that object, which is the thing-in-itself or noumena. Instead, I merely have
access to my own perceptions of that object, the phenomena or
appearances of that object.
reason Kant asks “How is pure natural science possible?” is
because if we do not have direct access to the noumena,
a serious problem arises: without direct access to
things-in-themselves, how are we supposed to 'know' about them?
our senses and our empirical intuition we can, argues Kant, create
subjective claims which Kant refers to as judgments
of perception. Being
subjective, these judgments of perception apply only to my personal
experience, only to the object or objects I am directly observing,
and only at the present time—they have no 'law-like' qualities.
solution Kant proposes to this dilemma is based around a set of a
concepts of understanding. These pure concepts of understanding have general, law-like qualities
and act to order our empirical experiences, into intelligible,
objective universal laws. By applying these pure concepts of
understanding to judgments of perception, we can create what Kant
calls judgments of experience: objective bits of knowledge about our
uses his pure concepts of understanding to get around many of the
problems posed by Hume. While he agrees with Hume about 'cause and
effect' as largely incomprehensible, saying, “Hume justly
maintains that we cannot comprehend by reason the possibility of
causality,” Kant also says that he is unwilling to say, as Hume
does, that concepts like 'cause and effect' arise from mere habit.
Instead, Kant claims, “On the contrary, I have amply shown that
they and the principles derived from them are firmly established a
argues that knowledge of the physical world, in other words natural
science, is 'possible' because, using pure concepts of understanding,
we can create from our own subjective experiences the objective,
intelligible natural laws necessary to make claims about the natural
What then of
Kant turns his attention to his original question, “Whether
such a thing as metaphysics be at all possible?” His answer is
Though there are,
and this is very important to Kant, strict boundaries on what
metaphysics can and cannot accomplish. In this way metaphysics is
different from both mathematics and natural science: both of these
fields have 'limits', but within those limits any question posed can,
at least in theory, be answered. But the field of metaphysics is
different, argues Kant. Because we have no 'experience' regarding the
questions we ask—questions which, for example, probe the nature and
existence of God, or souls, or look at the origins of the Universe—we
cannot come to specific conclusions regarding metaphysical questions.
But we can,
claims Kant, use the boundaries of metaphysics to see what may lie
beyond our realm of experience. And more importantly, we can recast
the study of metaphysics into something which focuses not on broad
questions which cannot be answered (due to our lack of experience),
but instead focuses on critiquing reason itself.
Was he right?
main weakness in Kant's Prolegomena
to Any Future Metaphysics is
Kant's argument that there can be a
judgments using the faculty of pure intuition. Kant give pure
intuition regarding space and time great importance, and in doing so
allows his argument to progress from a discussion regarding the
possibility of mathematics to a discussion on the possibility of
Kant's assertion that pure intuition is a
priori is problematic. Firstly, it is difficult, if not impossible to
separate the intuitions surrounding space and time from
experientially derived factors. Kant argues that space and time
cannot be things-in-themselves because they are a
but he neglects to give a sound argument as to why both space and
time must be a
this is where the major weakness in Kant's argument rests—his
shifting of time and space from things-in-themselves is in my opinion
brilliant, but it also is not adequately defended. Given this, I do
not believe that we can whole-heartedly accept Kant's conclusions in