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preciate reason in the interests of faith ; the latter take
reason as the only possible guide, but find no ground
for confidence in it. To the former class belongs
Nicholas of Cusa (1440), who was the author of two
sceptical treatises on human knowledge; certainty is
to be found, according to his view, only through the
mystical knowledge of God. The scepticism of Mon-
taigne made a reservation (whether sincerely or not is
uncertain) in favour of revealed truth ; and the same
principle was advocated by Charron, Sanchez, and Le
Vayer. Hume, in his sceptical essays on miracles and
immortality, also attributed a final authority to rev-
elation; but with obvious insincerity. The sceptical
views of Hobbes, combined with his peculiar theory
of government, made all conviction, including that of
religious truth, dependent on the civil authority.
Glanvill's "The Vanity of Dogmatizing", or "Scepsis
Scientifica", grounded a serious defence of revealed
religion on the uncertainty of natural knowledge.
Balfour's "Defence of Philosophic Doubt", based on
the indemonstrability of ultimate truths, is an at-
tempt in the same direction. (See Fideism.)
In the second class are to be reckoned the various systems of genuine scepticism. This appeared in Greek philosophy at a very early date. Heraclitus held the senses to be untrustworthy {Kami lidprvpes) and misleading, though he also conceived a supersen- suous knowledge of the universal reason, immanent in the cosmos, to be attainable. Zeno of Elea defended the doctrine of the unity and permanence of being by propounding a series of " hjrpotheses ", each of which resulted in a contradiction, and by means of them sought to demonstrate the unreality of the manifold and changing. The subjective principle of the Soph- ists (Protagoras, Gorgias, and others of less note) that "man is the measure of all things" implies doubt, or scepticism, as to all objective reality. Knowledge is resolved by Protagoras into mere variable opinion; and Gorgias asserts that nothing really exists, that if anything existed, it could not be known, and that if such knowledge were possible it would be incommuni- cable. The Pyrrhonists, or Sceptics, held everything in doubt, even the fact of doubting. The Middle Academics, whose chief representatives were Arcesi- laus and Carneades, while doubting all knowledge, held, nevertheless, that probability could be recog- nized in varying degrees. The "Encyclopedia" of Diderot and d'Alembert comments on the odd self- contradiction of Montaigne, who claimed a higher de- gree of probability for the Pyrrhonist than for the Academic opinion. Sextus Empiricus advanced the theory, often since maintained, that the syllogism is really a petitio principii, and that demonstration is therefore impossible. Bayle, in his celebrated " Dic- tionary", subjected the philosophy of his time to severe destructive criticism, but was confessedly un- able to supply its deficiencies. Hume's position was purely negative; for him, neither the existence of the external world nor that of the mind by which it is known was capable of demonstration ; and the conclu- sion of Kant's "Critique of Pure Reason", that the "thing in itself" {Ding an sich) is unknowable though certainly existing, is evidently .sceptical (though the author himself rejected the title), since it embodies a purely negative doubt as to the nature of "tran- scendent" reality. Kant's argument for the existence of God, as rationally indemonstrable, but postulated by the practical reason, necessarily results in a very limited conception of the Divine nature. Lamennais made general consent, or the common sense of man- kind, the only ground of certitude; the individual rea- son he held to be incapable of attaining it. " Nothing is so evident to us to-day that we can be sure we shall not find it either doubtful or erroneous to-morrow" (Essai sur I'indiffdrence, II, xiii).
It may be observed that theories which deny the validity of simple experience as a guide to truth are
really instances of doubt, because, though they assert
dogmatically the inadequacy of widely accepted evi-
dence, they are nevertheless in that state of suspense
by which doubt is properly characterized in regard to
the reality commonly held to be made known by ex-
perience. Thus the mental attitude which received
from Professor Huxley the name of Agnosticism is a
strictly doubtful one towards all that lies beyond
sense-experience. The doubt is purely negative in
this view; whatever is not cognizable by the aid of the
senses is held to be unknowable; God may exist, or
He may not, but we can neither affirm His existence
nor deny it. Again, the system or method known as
Pragmatism regards all reality as douljtf ul ; truth is the
correspondence of ideas with one another, and cannot
be regarded as anything final, but must perpetually
change with the progress of human thought ; knowl-
edge must be taken at its "face value" from moment
to moment, as a practical guide to well-being, and
must not be regarded as having any necessary corre-
spondence with definite and permanent reality.
Doubt in Reg.\rd to Religion has at different times assumed a variety of forms. It is perhaps uncertain how far the ancient mythologies received or even de- manded exact belief; it is at any rate certain that they were, as a rule, not considered worthy of serious atten- tion by the philosophers of any school. The atheism which formed part of the charge on which Socrates was condemned was an offence against the State rather than against religion in itself (see Lecky, Hist, of European Morals, ii). The faith demanded by the Christian Revelation stands on a different footing from the belief claimed by any other religion. Since it rests on Divine authority, it implies an obligation to believe on the part of all to whom it is proposed ; and faith being an act of the will as well as of the intel- lect, its refusal involves not merely intellectual error, but also some degree of moral perversity. It follows that doubt in regard to the Christian religion is equiv- alent to its total rejection, the ground of its accep- tance being necessarily in every case the authority on which it is proposed, and not, as with philosophical or scientific doctrines, its intrinsic demonstrability in detail. Thus, whereas a philosophical or scientific opinion may be held provisionally and subject to an unresolved doubt, no such position can be held towards the doctrines of Christianity; their authority must be either accepted or rejected. The unconditional, in- terior assent which the Church demands to the Divine authority of revelation is incompatible with any doubt as to its validity. Gregory XVI, by the Brief "Dum acerbissimas", 26 Sept., 1835, condemned the teach- ing of Hermes that all theological inquiry should be based on positive doubt (Denzinger, 10th ed., no. 1619); and the Vatican Council declared (Sess. II, ch. xxxi): "revelata vera esse credimus, non propter intrinsecam rerum veritatem naturali rationis lumine perspeetam, sed propter auctoritatem ipsius Dei reve- lantis, qui nee falli nee fallere potest", i. e. we believe the things that are revealed to be true, not because of an intrinsic truth which reason perceives, but because of the authority of God Who is the Author of Revela- tion, and Who can neither deceive nor be deceived.
Heresies have, however, generally had the character rather of dogmatic assertion than of mere doubt, though they arose from a more or less prevalent state of doubt as to doctrines imperfectly understood or not yet authoritatively defined. The devotion to classical studies which followed upon the fall of Constantinople in 1453 and the dispersion of its literary treasures gave rise to the humanism, or literary revival, of the Re- naissance, and in many cases resulted in a sceptical attitude towards religion. This scepticism, however, was by no means universal among the Humanists, and was due rather to lack of interest in theological, as compared with literary and philosophical, study, than to any reasoned criticism of religious doctrine. (See
