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. [Sidenote: _Scepsis and scepticism._] But the scepsis, which clears the ground of all forms of erroneous logical affirmation, is the negation of error and consequently the negativity of negativity. The negativity of negativity is affirmation, and for this reason, the true scepsis, like every true negation, always contains a positive content in the negative verbal form, which can be also verbally developed as such. If this positive content, instead of being developed, is choked in the bud, if instead of negation, which is also affirmation, a mere negation is given,--an abstract negation, which destroys without constructing, and if this negation claims to pass as truth, the final form of error is obtained, which is no longer called scepsis, but _scepticism._ [Sidenote: _Mystery._]