- Descartes.
Rene Decartes (1596-1650) turned skepticism into a method of doubt,
and uses Augustine's argument to refute his skepticism or doubt,
He decided to doubt everything that he could doubt, until he found
that could not be doubted. Though he could doubt all else, Descartes
could not reasonably doubt that he, who was thinking, exists.
"Cogito ergo sum." ["I think, therefore, I am."]
He concluded that he exists as a thinking thing, a res cogitans.
This intuition is self-evident, a clear and distinct idea. Another
idea that was also self-evident is the existence of the most
perfect Being, God.
Though he offered several proofs for Divine existence, he was
convinced that he knew this also as an innate idea, as a clear and
distinct idea. Since a perfect Being, God, could not deceive him
into believing that material bodies exist, when they did not, they
must exist. He concluded that human knowledge is fundamentally
reliable, provide we use it properly. For God, being good, would
not have endowed us with an ability inherently deceptive. We can
have confidence in Reason. Since the clear and distinct ideas on
which all certain knowledge rests are not arrived at by mere sense
observations, their source must be found in innate ideas; but there
is no suggestion in Descartes that they are memories left over from a
previous existence, like Plato's innate ideas. Innate ideas,
according to Descartes, are not in the mind at birth, but infants
are born with the facility of acquiring them. He nowhere gives a
list of these innate ideas; they evidently included the axioms of
mathematics, the laws of thought, and other propositions that he
treated as self-evident, such as a cause must have at least as much
reality as its effect and the certainty of one's own existence.
- Spinoza.
Bendict Spinoza (1632-1677) believed that the real and lasting
good can be experienced in love for what is eternal and infinite,
that is, God. But such a God must be a being of mathematical
necessity and scientific law. If a man can identify himself
with God conceived as the substantial underlying reality of all
of the processes of nature, which never has changed, and never
will change, he will posess an inward peace of mind which no one
can give or take away. In this "intellectual love of God" that
was conceived as the logical ground of the mechanical laws of
nature, Spinoza found his salvation. He built his religion upon
the science of his day as he understood it. His most important
book, the Ethics, is written like a book on geometry,
beginning with definitions, axioms, and postulates, and proceeding
through successive theorems, to which notes (scholia) are added.
Spinoza distinguished three kinds of knowledge: opinion, reason,
and intuitions. Opinions are ordinary observation of the senses
given in experience. These he considerd unreliable, and likely to
be erroneous. He had absolute confidence, on the other hand, in
reason and intuition. Reason is based on certain ideas that all
men have in common, and by reason propositions are proved by the
methods of geometry, and conclusions are derived from the premises
of a syllogism. Intuition "proceeds from an adequate idea of the
absolute essence of certain attributes of God to the adequate
knowledge of the essence of things." This means that if we know
anything through and through we will understand it in its ultimate
nature and necessity, and that is as some aspect of God. Our minds
in so far as they perceive things truly are part of the infinite
intellect of God; and our clear and distinct ideas are as necessarily
true as the ideas of God.
- Leibniz.
Gottfried Wilhelm Leibniz (1646-1716), in response to Locke's statement,
"Nihil est in intellectu quod non prius fuerit in sensu"
("Nothing is in the intellect which was not first in sense") added
"nisi intellectus ipse." ("except for the intellect itself.").
At birth the soul, far from being a tabula rasa ("blank tablet"),
is like the unworked block of marble, its hidden veins already
containing what it will become through the labor of the sculptor.
Leibniz distinguished between truths of reason and
truths of fact.
This was the contemporary distinct between analytic and synthetic
truths. The former rest on the Principle of Identity, since the
negation of a truth of reason is a contradiction. The latter rest
on the Principle of Sufficient Reason. The former have their source
in the mind as active, the latter in the mind as passive (that is,
as mirrowing the world). The former would be true in any possible
world. The latter are true in this world. The former are necessary,
the latter are contingent. Leibniz also distinguished between
absolutely necessary, the truths of reason, and hypothetical
necessary, truths of facts, that are true only in this world.
Certain necessities of latter kind, like causality, are given in
God's decision to create this world rather than some other.
Truths of reason are more basic than truths of fact. The
characteristic universalis (universal characteristic) is a
development of Leibniz' belief in the primacy of truths of reason.
The truths of reason are eternal truths (verites eternelles).
Examples are the principles of logic and mathematics and the
existence of God, which we know intuitively or by demonstration,
using the principles of identity and contradiction.
The principle of identity (A is A) enables us to recognize
the identity of the subject and predicate of a logical judgment.
The principle of contradiction assures us that it is
impossible for two mutually exclusive judgments, like A is B and
A is not B, to be both true in same sense.
These principles enable us to establish certain truths
as eternal. By means of eternal truths we can establish no
particular fact regarding existing things, with the exception of the
existence of God. Eternal truths (except the existence of God)
afford us only hypothetical judgments about existence; for example,
if a triangle exists anywhere, the sum of its angles must be equal
to two right angles. Our knowledge of existing events affords us
contingent truths, or truths of fact (verites du fait);
Leibniz concedes to the empiricists that such knowledge comes only
from observation. Yet, he says, for every existing fact there must
be a sufficient reason why it occurs as it does and why something
else did not take place instead. Leibniz advances the ontological
and cosmological arguments for the existence of God modified in
accordance with his own theory of knowledge. He also found an
argument in the pre-established harmony. These arguments for the
existence of God are not conclusive. The existence of God cannot
be demonstrated in a short series of propositions without leaving
a great many assumptions unexplained and undefended. If a
philosopher can present a system to us which is the most
satisfactory intellectually of any that we know, and if some
particular feature of his system, such as his conception of God,
is an integral part of it, we shall be disposed to accept this
feature because of the merits which we see in the system as a
whole. The problem with this approach is that it reduces God
to a secondary position and makes his existence dependent upon the
system. This is the problem of trying to prove God's existence;
the existence of God is just another theorem in the system. One
either begins with the existence of God as an axiom and postulate
of the system, not requiring any proof, or it is not God' and His
existence that is proved, but of something less than God.
- Kant.
Immanuel Kant (1724-1804) was trained in Leibnizian philosophy, as
presented by Christian Wolf (1679-1754). Wolf was influenced by
Leibniz,
whom Wolf knew personally, and by the
Cartesian
method of doubt that he sought to emulate in philosophy while remaining in
the Scholastic tradition. Wolf elaborated a philosophy that he believed
to follow rigorously from the principles of contradiction and sufficient
reason. Kant was a follower of Wolf until Hume roused him from his "dogmatic
slumber", from his rationalism. This lead Kant to poise the question,
"How are synthetic a priori judgments possible?" or, in other words,
"How are univeral and necessary judgments possible?" Kant poised his question
in the terminology current in philosophical literature since Leibniz, which
made a distinction between analytic and synthetic judgments, and
between a priori and a posteriori judgments.
A judgment is a proposition that is in the subject-predicate form.
An analytic judgment is one whose predicate merely asserts a
characteristic already implicit in the subject. For example, "All bachelors
are unmarried" is an analytic judgment because the predicate "unmarried" is
by definition contained in the subject of the proposition "All bachelors".
One has this information without examination of the world.
On the other hand, in a synthetic judgment the predicate is not
implicit in the subject; it adds something to the subject. For example,
"The house is red" is a synthetic judgment, because one would have to examine
the house to determine whether it is red.
Now analytic judments are a priori in the sense that we know their
truth or falsity prior to experience, that is, apart from, or without
experience.
But synthetic judgments are a posteriori in the sense that we know
the truth and falsity only after experience, that is, by means of, and through
experience.
Arranging these terms in a table, the meaning of Kant's question
becomes clear.
| Analytic |
A Priori |
| Synthetic |
A Posteriori |
The strength of analytic judgments lies in their necessity, and their weakness
is that they tell us nothing new. On the other hand, the strength of synthetic
judgments lies in their ability to tell us something new, and their weaknesses
in their having no necessity. If we could have judgments that would provide us
with both information and necessity, we would have the best of both worlds.
These would be synthetic a priori judgments, combining the strengths of
the synthetic and analytic judgments. Kant did not ask if the synthetic
a priori judgments are possible, but how are they possible,
because he thought that he had discovered such judgments in science, that is,
"4 + 2 = 6",
"a straight line is the shortest distance between two points",
"in all changes of the physical world the quantity of matter remains
unchanged",
"in all communication of motion, action and reaction must always be equal".
Kant arrive at the solution to his problem by what has been called a
Copernican revolution in philosophy. Copernicus was able to explain the
apparent motion of the planets by the motion of the observer. Kant was able
to explain how synthetic a priori judgments about the physical
world are possible by considering the nature of the knower. Thus our
knowledge of the apparent physical world (phenomena) is a combination
of two realities (noumena), the noumenal world and noumenal self. We
know only a phenomenal combination of noumenal realities, that is, behind the
apparent phenomenal world lies the noumenal reality, the world-in-itself, or
to use Kant's synonym for noumenon, Ding an Sich ["The thing
in itself"]. To ask "what this world is like apart from our observation of
it" is like asking, "How does it appear when it doesn't appear?"
The question is meaningless and is not intelligible. In conclusion, we are
to give up the attempt to know the noumenal world that we cannot know and
concentrate on knowing the phenomenal world that we do know.
Kant in considering the nature of knower concluded that the mind contributes
the forms of space and time to the raw data of sensation, and the categories
of the Understanding. To the manifold of sense we contribute not only space
and time, but structural elements of a conceptual nature. These categories
in which we think of the world comes from the structure of our understanding.
Everything sensed and understood has quality, quantity, relation, and
modality; the 12 basic categories are set forth in terms of these.
| Quantity |
Quality |
Relation |
Modality |
| Unity |
Positive |
Substance-accident |
Possibility-Impossibility |
| Plurality |
Negative |
Cause-effect |
Actuality-Nonactuality |
| Totality |
Limited |
Reciprocity or Community |
Necessity-Contingency |
Kant also find four sets of principles corresponding to the sets of terms:
Quantity - Axioms of intuition;
Quality - Anticipations of perception;
Relation - Analogies of experience;
Modality - Postulates of empirical thought.
Notice that Kant has gotten these categories out of classical
Aristotelian logic, and the three sets of terms under "Relation" are derived
respectively from categorical propositions with a subject-predicate
structure, hypothetical propositions with an if-then structure, and
disjunctive propositions with an either-or structure. The principle
relating to causality is that it is necessary for a man to view the world in
causal terms. The principle relating to reciprocity extends the idea of
causal interaction to a community of interacting substances.
According to Kant, knowledge is a product of both sense and understanding.
Kant points out that "thoughts without content are empty; and intuitions
without concepts are blind." Thus Kant produced an epistemology that
combines both empiricism and rationalism in which the limitations of each is
recognized. Kant held that the attempt to extend our ideas beyond
experience, called by Kant "dialectic", leads to contradiction. Kant lists
four of these Antinomies of Reason in which there are compelling
reasons for each position and its opposite. They are:
- The world has a beginning in time, and is limited with regard to space;
- Everything compound consists of simple parts, and nothing exists anywhere
but the simple, or what is compounded of it;
- There is freedom in the world, and not everything takes place according
to laws of nature;
- There exists an absolutely necessary Being belonging to the world either
as a part of it, or as the cause of it.
When one shifts to the opposite position, there are equally compelling
reasons for shifting back. Hence neither of the positions will do. The
corrective to this situation lies, of course, in refraining from posing
questions whose answers would require our going beyond possible experience.
This corrective consists in regarding ideas as regulative principles, having
no application beyond the reach of possible experience. These antinomies of
The Critique of Pure Reason push thought beyond Understanding and
toward Reason (Vernunft); that is, thought is calling for a
completeness which goes beyond the phenomenial world. Reason (Vernunft)
is a power to systematize into an unity on the basis of the most inclusive
principles. This most inclusive standpoint involves the Ideas of Reason:
God, freedom, and immortality (in contrast to the categories of the
Understanding). In his The Critique of Practical Reason Kant works
out this standpoint. These Ideas of Reason are practically warranted
although not theoretically demonstrable. They are simply regulative, that is,
forms of ideal construction with no demonstrative metaphysical import.
Conclusion: The dramatic conclusion of Kant's theory of knowledge is
that we can never know the "real" nature of the external world or any
object in it, if by "external world" we mean the world independent
of human knowledge. What we do know are the appearances (phenomena)
produced by the operation of the space-time forms of the mind.
Things-in-themselves (noumena) are unknowable and forever hidden
from us. There is really no way we can know whether our concepts really
correspond to things-in-themselves. This is a just another form of
skepticism. Kant's philosophy has sometimes been called Transcendental
Idealism, but Kant himself rejected the description of his philosophy as
Idealism, as he understood the term. To him his system was Critical Philosophy
or Transcendental Philosophy.
- Absolute Idealism.
In the early nineteenth century the German philosophers, Fichte, Schelling,
and Hegel all challenged and rejected Kant's doctrine of the limitations of
human knowledge. On the basis of what Kant had himself admitted as the
function of reason, they pressed beyond the limitations that Kant had laid
down. Kant's Critical Philosophy failed to satisfy their demand for ultimate
unity. Kant's philosophy appeared to be dualistic with its distinction
between the phenomena, as the knowable, and the noumena, as unknowable
things-in-themselves. They all accepted as fundamental that reality was a
systematic unity knowable by human reason. Reason cannot halt with the
partial and incomplete, pointing beyond itself. The ideal of Reason must
inevitably be a complete system, each and every constitutent of which
fitting rationally with every other.
- Fichte.
Johann Gottlieb Fichte (1762-1814) was strongly infuenced by Kant and
is considered to be the founder of German Idealism. He derived his philosophy
from Kant by making practical reason determinative over theoretical reason, a
step which Kant himself did not seem to make. Fichte started by arguing for
the freedom of the will. For Kant, the primacy of the moral is a matter of
postulates; we are to act as if the maxim on which we act
were a law of nature; as if our wills were free; as if we
were immortal; as if there was a God. In Ficte's thought. the
as if disappears. The moral law is is the law of nature;
our wills are free; our souls are immortal. God exists
as the moral order of the universe. The Kantian postulation has been
replaced by Fichtean affirmations. The whole external physical world
is the material of duty made manifest to our senses. Fichte
argued; if everything happens by causal necessity, then we are
not responsible for either good or evil that we do; for the source of our
action will be nature, and not ourselves. He argued that causal necessity,
which we at first seem to see in nature, exists only in our own thought;
therefore we need not to take necessity or nature as seriously as we did
initially. Indeed, moral consciousness, telling us that we are free and alone
responsible for our actions, is not in the same class as our positing of
causality and is given primacy over the nature and causality. Moral ideals
are more determinative of our actions than causality. Fichte called this
philosophy that gave the primacy to moral ideals "Idealism" and its
opposite "Dogmatism."
It was also Fichte, not Hegel, who first presented the process of the
dialectic as consisting of Thesis, Antitheses, and Synthesis,
and so-named the stages. The activity of reason itself requires that
posit, counterposit, and synthesis mark its progress.
- Schelling.
The German philosopher Friedrich Wilhelm Joseph Schelling (1775-1854)
gave the name "subjective idealism" to the philosophy of Fichte, since in
Fichte's philosophy the world is posited by the judging subject. In his
middle stage, Schelling called his own philosophy "objective idealism," for
he held that nature is simply "visible intelligence." Thus the term "idealism"
came to be applied to all philosophies that identified reality with idea,
reason, or spirit. Idealism had become Ideaism.
- Hegel.
The German philosopher Georg Wilhelm Fredrich Hegel (1770-1821) accepted
the classification of Schelling's, but putting it to his own use. Holding
subjective and objective idealism to represent thesis and antithesis,
respectively, Hegel presented his philosophy as the higher synthesis of these
positions, which he called "Absolute Idealism." Absolute Idealism made clear
that rationalism is more than an epistemological position; Hegel showed that
it is a metaphysical view, by asserting that the real is rational and the
rational is the real. That is, Hegel identified the rational and the real,
and made explicit the metaphysical foundation of rationalism. Hegel was
influenced by the rationalism of Spinoza and Kant, and the idealism of Fichte
and Schelling; but he developed their rationalism and idealism by identifying
reason and reality ("The real is the rational; the rational is the real"),
and by understanding reason as the Dialectic; that is, out of
the contrariety of the Thesis and Antithesis comes a Synthesis, which becomes
the Thesis of a new level of the development of the Dialectic.
The nineteenth century Idealists who succeeded Hegel developed the
Coherence Theory of Truth (that is, the truth is the coherent
system of ideas or propositions; a proposition is true if it coheres with
the system of all true propositions) to expand the meaning of rationalism to
include the concept of "system". While not always clear what a system is,
these philosophers saw that the truth of a proposition could not be
established apart from the system of all true propositions.