There is a form of scepticism which would like to appear critical and refined and which takes the name of _agnosticism._ It is a scepticism limited to ultimate things, to profound reality, to the essence of the world, which amounts to saying that it is limited to the supreme principles of philosophy. Now, since the principles of philosophy are all equally supreme, such agnostic scepticism extends its affirmation of mystery over neither more nor less than the whole of philosophy and consequently over the whole of human knowledge. Its limits would be nothing less than the boundaries of knowledge. Indeed, agnosticism is the spiritual fulfilment sought by all those who negate philosophy, such as æstheticists, mathematicians, and especially empiricists; and agnostics and empiricists are ordinarily so closely connected that the one name is almost synonymous with the other. [Sidenote: _Mysticism._] The sceptical error, which consists in stating the problem as solution and mystery as truth, can give way to another mode of error, in which the very affirmation of scepticism is denied and it is recognized that thought cannot explicitly state mystery. But this recognition, which would imply that of the authority of thought, is strangely combined with the most precise negation of such authority. Thought being excluded, either affirmatively or negatively, as in the self-contradiction of scepticism, what remains is life, no longer a problem, or a solution of a problem, but just life, life lived. To affirm that truth is life lived, reality directly felt in us as part of us and we part of it, is the pretension of _mysticism._ This is the last general form of error that can be thought; and its self-contradiction is evident from the genetic process which we have already expounded. Mysticism affirms, when no affirmation is permitted to it; and it is yet more gravely contradictory than scepticism, which, though forbidding to itself logical affirmation, does not forbid itself speech, that is to say, æsthetic expression. To mysticism not even words can be permissible, because mysticism, being life and not contemplation, practice and not theory, is by definition _dumbness._ But we shall say no more of mysticism, having had occasion to refer to it, as also to æstheticism and empiricism, at the beginning of this treatise on Logic. [Sidenote: _Errors in the other parts of philosophy._]