[25] For Aristotle the principle of individuation was matter and form (vid. note, p. 33); for Averroes it was form; for St Thomas it was matter. For all “vitalists” the identity of form, soul and life is essential; thus Stahl regarded soul as bestowing on body all activity, as determining all vital functions. In Aristotle ψυχή is untranslatable = anima and animus—soul and vital principle. Πνεῦμα again in various writers may mean anything, from air to spirit or other essence; cf. Arist. De Generat. An. II. 3, and the “aura” of Harvey, and even of Haller in the same connexion as the fertilising element. [26] Not for all, not for the greatest of them! Aristotle, in vain, warned later generations against prophesying what seems likely, instead of looking to see how things come about:—“οὐκ ἀληθῆ λέγοντες, ἀλλὰ μαντευόμενοι τὸ συμβησόμενον ἐκ τῶν εἰκότων, καὶ προσλαμβάνοντες ὡς οὕτως ἔχον πρὶν γινόμενον οὕτως ἰδεῖν.” (De Gen. Anim. IV. i.) “Croire tout ce qu’on rêve,” if useful and possibly admirable in its day, in “neo-Hegelians” is a little stale. [27] Thus, in ascending from general to more general, in the most general will be sought unique and perfect being; the primary cause and sole object of science—the αὐτοζῷον of the Alexandrians: whereas by successive eliminations utter abstractions would become utter vacuity. To such realists all subordinate beings are integral parts of the primary being. It would serve no useful end here to analyse these doctrines, or to indicate the pythagorean or stoical elements of them; for platonists and realists had their schools and degrees of subtlety; and Plato himself was inconsistent. Some brought secondary agents—demiurges or angels—into more creative activity, others carried creative reason back to the ideal good, and so on. [28] Held by Gilbert, and attributed to Averroes; but older than Averroes. In turning to Francis Bacon’s hypothesis I read (Ed. E. and S. II. 263. Hist. Densi et rari—chapter, “Dilatationes per spiritum innatum se expandentem,” a Paracelsian sort of chapter) “Pulsus cordis et arteriarum in animalibus fit per irrequietam dilatationem spirituum, et receptum ipsorum, per vices.” The muscular quality of the heart was known to Galen, forgotten, and rediscovered. Spiritus vitalis, for Bacon, was “aura composita ex flamma et aere” (cf. Æn. VI. 747). Glisson has been fortunate in two generous judges, in Haller and Virchow; it would ill become me to depreciate a distinguished Fellow of my own College, and as a clinical observer Glisson had considerable merits; but as a physiologist he was sunk in realism. He was happy in the invention of the technical term “irritability,” but for him this virtue was as metaphysical an essence as the vital spirit; his prime motor was not physical. As a philosopher I fear the independent reader of his works will find him fanciful and wearisome.