In carrying out this theory, they could not, as might be expected, wholly succeed. Hence a Stoic could not deny that there are certain things which it is absurd to call material. Among such include empty space, place, time, and expression (λεκτόν). [269] Admitting these to be incorporeal, they still would not allow that they do not exist at all. This view belongs only to isolated members of the Stoic School, for which they must be held personally responsible. [270] How they could harmonise belief in incorporeal things with their tenet that existence alone belongs to what is material is not on record. [(2) Causes which produced the Stoic materialism.] The question next before us is: What led the Stoics to this materialism? It might be supposed that their peculiar theory of knowledge based on sensation was the cause; but this theory did not preclude the possibility of advancing from the sensible to the super-sensible. It might quite as well be said that their theory of knowledge was a consequence of their materialism, and that they referred all knowledge to sensation, because they could allow no real being to anything which is not material. The probability therefore remains that their theory of knowledge and their materialistic view of nature both indicate one and the same habit of mind, and that both are due to the action of the same causes. [(a) The Stoic materialism not an expansion of Peripatetic views.] Nor will it do to seek for these causes in the influence exercised by the Peripatetic or pre-Socratic philosophy on the Stoic School. At first sight, indeed, it might appear that the Stoics had borrowed from Heraclitus their materialism, together with their other views on nature; or else their materialism might seem to be an expansion of the metaphysical notions of Plato and Aristotle. For if Aristotle denied Plato’s distinction of form and matter to such an extent that he would hardly allow form to exist at all except in union with matter, might it not appear to others more logical to do away with the distinction between them in thought, thus reducing both to a property of matter? Were there not difficulties in the doctrine of a God external to the world, of a passionless Reason? Were there not even difficulties in the antithesis of form and matter, which Aristotle’s system was powerless to overcome? And had not Aristoxenus and Dicæarchus before the time of Zeno, and Strato immediately after his time, been led from the ground occupied by the Peripatetics to materialistic views? And yet we must pause before accepting this explanation. The founder of Stoicism appears, from what is recorded of his intellectual growth, to have been repelled by the Peripatetic School more than by any other; nor is there the least indication in the records of the Stoic teaching that that teaching resulted from a criticism of the Aristotelian and Platonic views of a double origin of things. Far from it, the proposition that