Of a more formal type is that second kind of essential collision, an illustration of which in the tragic story of Œdipus the Greek tragedians especially favoured. Of this Sophocles has left us the most complete example in his "Œdipus Rex," and "Œdipus in Colonos." The problem here is concerned with the claim of alertness in our intelligence, with the nature of the obligation[47] implied in that which a man carries out with a volition fully aware of its acts as contrasted with that which he has done in fact, but unconscious of and with no intention of doing what he has done under the directing providence of the gods. Œdipus slays his father, marries his mother, begets children in this incestuous alliance, and nevertheless is involved in these most terrible of crimes without active participation either in will or knowledge. The point of view of our profounder modern consciousness of right and wrong would be to recognize that crimes of this description, inasmuch as they were neither referable to a personal knowledge or volition, were not deeds for which the true personality of the perpetrator was responsible. The plastic nature of the Greek on the contrary adheres to the bare fact which an individual has achieved, and refuses to face the division implied by the purely ideal attitude of the soul in the self-conscious life on the one hand and the objective significance of the fact accomplished on the other. For ourselves, to conclude this survey, other collisions, which either in general are related to the universally accepted association of personal action to the Greek conception of Destiny, or in some measure to more exceptional conditions, are comparatively speaking less important.