Most 18th-century thinkers gave up the quest for metaphysical knowledge

after imbibing Bayle's arguments.

George Berkeley, an Empiricist and Idealist, fought Skeptical doubts by

identifying appearance and reality

and offering a spiritualistic metaphysics. He was immediately seen as

just another Skeptic since he was denying

the world beyond experience.

Bayle's chief 18th-century successor was David Hume. Combining empirical

and skeptical arguments, Hume

charged that neither inductive nor deductive evidence could establish the

truth of any matter of fact. Knowledge

could only consist of intuitively obvious matters or demonstrable

relations of ideas but not of anything beyond

experience; the mind can discover no necessary connections within

experience nor any root causes of experience.

Beliefs about the world are based not upon reason or evidence nor even

upon appeal to the uniformity of nature

but only on habit and custom. Beliefs cannot be justified. Belief that

there is an external world, a self, a God is

common; but there is no adequate evidence for it. Although it is natural

to hold these convictions, they are

inconsistent and epistemologically dubious. "Philosophy would render us

entirely Pyrrhonian, were not Nature

too strong for it." The beliefs that a man is forced to hold enable him

to describe the world scientifically, but

when he tries to justify them he is led to complete Skepticism. Before he

goes mad with doubts, however, Nature

brings him back to common sense, to unjustifiable beliefs. Hume's fideism

was a natural rather than a religious

one; it is only animal faith that provides relief from complete doubt.

The religious context of Skepticism from

Montaigne to Bayle had been removed, and man was left with only his

natural beliefs, which might be

meaningless or valueless.

The central themes in Hume's Skeptical analysis--the basis of induction

and causality, knowledge of the external

world and the self, proofs of the existence of God--became the key issues

of later philosophy. Hume's

contemporary Thomas Reid hoped to rebut Hume's Skepticism by exposing it

as the logical conclusion of

the basic assumptions of modern philosophy from Descartes onward. Such

disastrous assumptions should be

abandoned for commonsensical principles that have to be believed. As Hume

and Kant saw, Reid had not

answered Hume's Skepticism but had only sidestepped the issue by

appealing to commonsensical living. This

provided, however, neither a theoretical basis for beliefs nor a

refutation of the arguments that questioned them.

Kant saw that Hume had posed a most fundamental challenge to all human

knowledge claims. To answer

him, it had to be shown not that knowledge is possible but how it is

possible. Kant combined a Skepticism

toward metaphysical knowledge with the contention that certain universal

and necessary conditions are involved

in having experience and describing it. In terms of these it is possible

to have genuine knowledge about the forms

of all possible experience, space and time, and about the categories in

which all experience is described. Any

effort to apply this beyond all possible experience, however, leads into

contradictions and Skepticism. It is not

possible to know about things-in-themselves nor about the causes of

experience.

Though Kant thought that he had resolved the Skeptical problems, some of

his contemporaries saw his

philosophy as commencing a new Skeptical era. G.E. Schulze (or

Schulze-Aenesidemus) a notable critic

of Kantianism, insisted that, on Kant's theory, no one could know any

objective truths about anything; he could

only know the subjective necessity of his views. The Jewish critic

Salomon Maimon contended that,

though there are such things as a priori concepts, their application to

experience is always problematical, and

whether they apply can only be found through experience. Hence, the

possibility of knowledge can never be

established with certainty. Assured truth on the basis of concepts is

possible only of human creations, like

mathematical ideas, and it is questionable whether these have any

objective truth. The thesis that human creativity

is the basis of truth, however, was soon to be developed by Johann G.

Fichte, a leading German Idealist,

as a new way of transcending Skepticism.

Another Skeptical critic of Kant, J.G. Hamann, saw in Hume's and Kant's

work a new basis for fideism.

If knowledge of reality cannot be gained by rational means, t