Nothing can move itself. While it is true that the form of a thing determines the kind of motion it shall have, it cannot in itself produce that motion, which can be caused only by an efficient cause from without. The case of animal motions may seem like a refutation of this view, but it is not really so. The soul and the body are two distinct principles in the animal; and it is the soul that moves the body. The reason why a thing cannot move itself is because the thing which is moved is potential with reference to that which the motion is intended to realize, whereas the thing causing the motion is actual with respect to the relation in question. If then a thing moved itself, it would be actual and potential at the same time and in the same relation, which is a contradiction. The Bible, too, hints at the idea that every motion must have a mover by the recurring questions concerning the origin of prophetic visions, of the existence of the earth, and so on. Such are the expressions in Job (38, 36, 37): "Who hath put wisdom in the inward parts?" "Who can number the clouds by wisdom?" In Proverbs (30, 4): "Who hath established all the ends of the earth?" and in many passages besides.[234] The question of infinity is another topic of importance for proving the existence of God. We proceed as follows: An infinite line is an impossibility. For let the lines _a_------------_b_ be infinite in the _c_------|-----_d_ _e_ directions _b_, _d_. Take away from _cd_ a finite length = _ce_, and pull up the line _ed_ so that _e_ coincides with _c_. Now if _ed_ is equal to _ab_, and _cd_ was also equal to _ab_ by hypothesis, it follows that _ed_ = _cd_, which is impossible, for _ed_ is a part of _cd_. If it is shorter than _cd_ and yet is infinite, one infinite is shorter than another infinite, which is also impossible. The only alternative left is then that _ed_ is finite. If then we add to it the finite part _ce_, the sum, _ce_ + _ed_ = _cd_, will be finite, and _cd_ being equal to _ab_ by hypothesis, _ab_ is also finite. Hence there is no infinite line. If there is no infinite line, there is no infinite surface or infinite solid, for we could in that case draw in them infinite lines. Besides we can prove directly the impossibility of infinite surface and solid by the same methods we employed in line.