This perpetual transition from one form of error to another gives rise to a _scepsis,_ which promotes the reciprocal dissolution of errors, and scorning illusions and confusions, throws their _mental vacuity_ into clear light. Such a scepsis fulfils an important function. The lies of æstheticism, mathematicism, philosophism, mythologism, cannot resist it. Their little wordy strongholds are broken into; the shadows are dispersed. Especially against mythologism, which in a certain sense may be called the most complete negation of thought, a scepsis is helpful; and owing to the resistance offered here more than elsewhere, by passions and interests, it often takes the form of violent satire. The last great epoch of this strife is what is called the _Aufklärung,_ Encyclopedism or Voltaireism, and was directed against Christianity, especially in its Catholic form. We must make so many reservations in what follows concerning the enlightened Encyclopedist and Voltairean attitude, that here we feel obliged to indicate explicitly its serious and fruitful side.
[Footnote 1: See with reference to this G. Gentile, _Il modernismo e l'enciclica, Critica,_ vi. pp. 208-229.]
Total scepticism can be reached only through _dualism,_ which, in addition to being a particular error in a given philosophic problem, is a logical error, consisting in the attempt to affirm two methods of truth at the same time--the philosophic method and the non-philosophic method, however the second of these be afterwards determined. Such an error would not be error but supreme truth, if the various methods were given each its due post (which is what has been attempted in this Logic); but it becomes error when the various methods are made philosophical and placed _alongside_ the philosophical. This is the error of those conciliatory people, who, unwilling to seek out where reason stands, admit that reason is operative in all of them, and divide the kingdom of truth amongst all in equal parts. Thus arise those logical doctrines which demand for the solution of philosophic problems, the successive or contemporaneous application of the naturalistic method, of mathematics, of historical research, and so on. At the least they demand the combination of the naturalistic method (empiricism) with the speculative and the use of what they call the double criterion of _teleology_ and _causality,_ or of _double_ causality. To the question, what is reality, they reply with two methods and consequently offer two concurrent and parallel realities. Beneath the appearance of treatment and solution, they abandon the philosophic problem. Instead of conceiving, they describe, and description is given as concept, and concept as description: hence the justifiable intervention of the scepsis.