everything capable of acting or being acted upon must be material, appears with the Stoics as an independent axiom needing no further proof. [(b) The Stoic materialism not due to Heraclitus.] The supposed connection between the Stoics and Heraclitus, so far from explaining their materialistic views, already presumes their existence. Yet long before Zeno’s time the philosophy of Heraclitus as a living tradition had become extinct. No historical connection therefore, or relation of original dependence, can possibly exist between the two, but at most a subsequent perception of relationship can have directed Zeno to Heraclitus. Zeno’s own view of the world was not a consequence, but the cause, of his sympathy with Heraclitus. In short, neither the Peripatetics nor Heraclitus can have given the first impulse to Zeno’s materialism, although they may have helped in many ways to strengthen his views on that subject, when already formed. [(c) Practical turn of the Stoic philosophy the cause.] The real causes for these views must therefore be sought elsewhere, and will be found in the central idea of the whole system of the Stoics—the practical character of their philosophy. Devoting themselves from the outset with all their energies to practical enquiries, the Stoics in their theory of nature occupied the ground of common views, which know of no real object excepting what is grossly sensible and corporeal. Their aim in speculation was to discover a firm basis for human actions. [271] In action, however, men are brought into direct and experimental contact with objects. The objects thus presented to the senses we are brought face to face with in naked reality, nor is an opportunity afforded for doubting their real being. Their reality is proved practically, inasmuch as it affects us and offers itself for the exercise of our powers. In every such exercise of power, both subject and object are always material. Even when an impression is conveyed to the soul of man, the direct instrument is something material—the voice or the gesture. In the region of experience there are no such things as non-material impressions. This was the ground occupied by the Stoics: a real thing is what either acts on us, or is acted upon by us. Such a thing is naturally material; and the Stoics with their practical ideas not being able to soar above that which is most obvious, declared that reality belongs only to the world of bodies. [(3) Consequences of the Stoic materialism.]