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CRITIQUE OF PURE REASON
Arnel O. Rivera
Based on the presentation of:
Mr. Alexander Rodis
A PRIORI AND A POSTERIORI KNOWLEDGE
Kant distinguishes between empirical and a
posteriori knowledge derived from sense experience
and pure or a priori knowledge which is completely
independent of experience.
1. A PRIORI KNOWLEDGE is the knowledge which
comes before (prior to) sense experience and is
therefore independent of sense experience. This is the
emphasis of the rationalist.
Ex. “Justice is good.”
“All triangles have three sides.”
2. A POSTERIORI KNOWLEDGE is knowledge which
comes after (posterior to) sense experience and is
therefore dependent on sense experience. This is the
Ex. "There is a cup on this table."
“All swans are white."
He establishes the two identifying marks
by which pure or a priori knowledge may be
recognized and distinguished from
empirical or a posteriori knowledge:
If we have a proposition which in being
thought is thought as necessary, it is an a
priori judgment; and if, besides, it is not
derived from any proposition except one
which also has the validity of a necessary
judgment, it is an absolutely a priori
Experience never confers on its judgments
true or strict but only assumed and comparative
universality, through induction. We can properly
only say, therefore, that so far as we have
previously observed, there is no exception to this
or that rule. If, then, a judgment is thought with
strict universality, that is, in such manner that no
exception is allowed as possible, it is not derived
from experience, but is valid absolutely a priori
Empirical universality is only an arbitrary extension of a
validity holding in most cases to one which holds in all, for
instance, in the proposition, 'all bodies are heavy'. When,
on the other hand, strict universality is essential to a
judgment, this indicates a special source of knowledge,
namely, a faculty of a priori knowledge.
Necessity and strict universality are thus sure criteria of a
priori knowledge, and are inseparable from one another.
But since in the employment of these criteria the
contingency of judgments is sometimes more easily shown
than their empirical limitation, or, as sometimes also
happens, their unlimited universality can be more
convincingly proved than their necessity, it is advisable to
use the two criteria separately, each by itself being
HE DISTINGUISHES BETWEEN ANALYTIC AND
SYNTHETIC PROPOSITION OR KNOWLEDGE
They are knowledge that is true by definition but
not bearing on reality.
When this type of knowledge is express in the
proposition, the predicate is contained in the
They are logically true, and this means you could
not deny them.
This is an A is A type of proposition.
Ex. All barking dogs bark.
All triangles have three sides.
They are knowledge that is not logically certain, but
bearing on reality.
In synthetic proposition, the predicate adds something
to the subject, and thus two ideas are “synthesized” in
the proposition. It affirms or denies the existence of
something and it informs us about things, it really
does tell us something about the actual universe.
This is an A is B type of proposition.
Ex. It is snowing in Alaska.
Water freezes at 32 degrees Fahrenheit
SYNTHETIC A PRIORI KNOWLEDGE
Both rationalist and empiricist accept analytic
propositions as a priori certain and that they both at
least some accept the synthetic proposition as a
But can we possess any knowledge that is both a priori
certain and synthetically informative?
IS THERE SYNTHETIC A PRIORI KNOWLEDGE?
ACCORDING TO KANT, YES!
He explains the nature of synthetic a priori
knowledge both as being existentially informative and
also bearing the marks of necessity and universality,
something unaccountable for on the basis of
The ideas such as substance and causality do not make
their way into our minds through experience, but are
“a priori categories of the understanding”, which molds
and shape and in fact constitute our experience.
That is substance and causality are part of what we
Ex. “Every event must have a cause”
It is a synthetic truth but also possess a priori
universality and necessity.
We have to experience things as causally related
because that is the only way the mind create
Although our knowledge begins with experience, it
does not follow that it arises from experience. For it is
possible that even our experience is a compound of
that which we receive through impressions, and of that
which our own faculty of knowledge (incited only by
sensuous impressions) supplies from itself.
He insisted the role of a priori concepts as conditions
of experience and the epistemological consequences of
“If by them only it is possible to think any object
of experience, it follows that they refer by
necessity and a priori to all objects of experience.”
Synthetic a priori judgments are characterized by :
(a) an a priori element which is universal and
(b) an empirical element which applies to the world.
“Synthetic a priori judgments are only possible when
we relate the formal conditions of a priori intuition,
the synthesis of imagination and the necessary unity
of this synthesis in a transcendental apperception, to a
possible empirical knowledge in general ”.
Thus there is in the "synthetic a priori" that which is
not derived from experience, but yet applies to
There are synthetic a priori judgments:
(1) We have these in mathematics
(2) We have these in Physics: the concept of cause:
"Everything which happens has its cause."
(3) We ought to have these in Metaphysics
"The world must have a first beginning.”
Metaphysics ought to contain nothing but a priori
synthetic judgments - Thus the general problem of
Metaphysics becomes the general problem of a priori
THE LIMITS OF REASON
One of the implications of Kant’s analysis is that we can know
nothing of reality as it is in itself (what Kant calls the noumenal
world) but only as it appears to us through experience (he calls
this the phenomenal world)
The reason is clear: The a priori categories or concepts of the
understanding are constitutive of experience, and therefore they
have no legitimate application beyond experience.
Causality for example applies only to objects of possible
experience. And when we try to apply such concepts beyond
experience, what results in nonsense and absurdities.
Thus if we have gained a priori certainty and universality for
synthetic knowledge, it has been at the cost of giving up any
possible knowledge of reality beyond space and time.