The intellectual action in this crisis is marked by four forms;—(1) the criticism created by the scholastic philosophy, which has been thought to mark in Abélard the commencement of doubt; (2) the introduction of the idea of progress in religion, in the sense that Christianity is to be replaced by a better religion; (3) the idea of the comparison of Christianity with other religions, so as to obliterate its exceptional character; (4) the traces of disbelief in the doctrine of immortality. The two former are free thought as doubt, the two latter as disbelief. It will be necessary, for illustrating the first of those forms, to explain the nature of the scholastic philosophy, so far as to show how it might become the means of producing heresy or scepticism, when applied to theology. Scholasticism is the vague name which describes the system of inquiry common in the middle ages.(254) In truth it marks a period rather than a system; a method rather than a philosophy. In spite of difference of form, it links itself with the speculations of other ages in community of aim, in that it strove to gain a general philosophy of the universe, to reach some few principles which might offer an interpretation of all difficulties. In the present age the science which attempts this grand problem is denominated Logic, or Metaphysics, according to the different sphere which it covers.(255) But in the middle ages these two fields were not clearly distinguished; in the same manner as in the Διαλεκτικὴ of Plato, method and the realities attained by method were not separated.(256) Yet it was mainly in reference to the former that scholasticism wears the aspect of a method, and to the latter the aspect of a philosophy. Adopting deduction as the type of a perfect science, it assumed its data partly on the ground of innate ideas, partly from the truths of revelation, partly from the metaphysical dicta of Aristotle; and from these principles attempted to work out deductively a solution of universal nature. It was the Σοφία of Aristotle executed from a Christian point of view. In respect to the logical method there was a general agreement of opinion, but difference of system arose in the metaphysical. The form that the problem of science then assumed was peculiar. Instead of examining the data from which deduction starts, with a view of finding their subjective certainty as thoughts, the inquirers strove to settle the problem of their objective nature as things. The question asked was this: Are the genera and species which the mind contemplates, in its attempts to classify and interpret phenomena, real in nature, or produced only by human thought and speech? A comparison with the modern mode of investigation will explain the importance which the question possessed, and the reason why it monopolized the entire field of inquiry.