Such are the probable precedents, or as the common but inaccurate metaphor expresses it, "sources" of Vico's theory of knowledge. I do not think that the formation of this theory can have been influenced by the propositions of Geulinx and Malebranche which have been pointed out to me,[32] namely that "no one can make that which he does not know," and that "God alone knows his works, because he foreknows his action." In these propositions the old Thomistic doctrine is substantially summarised. Much more tenable would be a connexion or at least a comparison with Spinoza; we may recall the Spinozistic identification of the _ordo et connexio idearum_ and the _ordo et connexio rerum._ Another ingenious, but I think, inaccurate view is that "the analytic geometry of Descartes was the introduction of the genetic principle into the study of geometrical objects," so that the principle _verum ipsum factum_ "before being formulated by Vico had been practised by Descartes"; and Vico in the _De antiquissima_ "adopted the scientific method of Descartes, which he stated as the convertibility of the true with the created," raising it "from a certitude to a criterion."[33] We are dealing here not with practice, but simply with the theory of method: for this method, conceived in its universality, just so far as it is practical has always been practised; not by Descartes alone, and not only by analytic geometry. We should certainly be better informed as to the precedents of Vico's criterion if we knew more of his studies preparatory to the _De antiquissima,_ and if in general we had more literary evidence about his youth. Perhaps even the precedents I have indicated, which I only called probable, are not quite free from an element of chance; they may be connexions only imagined by myself and non-existent for Vico's mind, while others not accidental may perhaps be still unknown, or await discovery by a student more fortunate than myself. But it may not be out of place to remark that the search for "precedents" does nothing to explain the new thought that followed them; much less does it detract from the value of that thought. Such information, though on the one hand it enriches our knowledge of the history of philosophy, on the other hand has absolutely no effect upon the determinate thought under examination. It is valuable in the biography of a philosopher, but valueless for the comprehension of the proper meaning of the new theory, which must be sought essentially in the new problem which it faces and attempts to solve. In the history of philosophy the same principles hold good as in that of literature. Take for example the episode of Argante and Tancred in canto xix. of "Jerusalem Delivered"; Argante, while taking up his position for the fight with his adversary, turns "as if in doubt" to the "afflicted city," towards Jerusalem attacked by the crusaders; and when Tancred brutally mocks him, asking whether he does this out of fear, he replies:--