If matter participated in the existence of genuine beings and received them within itself, as might easily be thought, that which would enter into it would penetrate deeply into matter; but evidently matter is not penetrated thereby, remaining unreceptive of any of it. On the contrary, matter arrests their "procession," as echo arrests and reflects sound-waves, matter being only the "residence" (or, "jar" or vase) of the things that enter within it, and there mingle with each other. Everything takes place there as in the case of persons who, wishing to light fire from the rays of the sun, should place in front of these rays polished jars filled with water, so that the flame, arrested by the obstacles met within, should not be able to penetrate, and should concentrate on their outside. That is how matter becomes the cause of generation; that is how things occur within it. THE RELATION OF MATTER TO REASON ILLUSTRATED BY THAT OF OPINION AND IMAGINATION. 15. The objects that concentrate the rays of the sun, are themselves visible, by receiving from the fire of sensation what takes fire in their hearth. They appear because the images that form themselves are around and near them, and touch each other, and finally because there are two limits in these objects. But when the ("seminal) reason" is in matter, it remains exterior to matter in an entirely different manner; it has a different nature. Here it is not necessary that there be two limits; matter and reason are strangers to each other by difference of nature, and by the difference between their natures that makes any mixture of them impossible. The cause that each remains in itself is that what enters into matter does not possess it, any more than matter possesses what enters into it. That is how opinion and imagination do not mingle in our soul,[75] and each remains what it was, without entailing or leaving anything, because no mingling can occur. These powers are foreign to each other, not in that there is a mere juxtaposition, but because between them obtains a difference that is grasped by reason, instead of being seen by sight. Here imagination is a kind of phantom, though the soul herself be no phantom, and though she seem to accomplish, and though she really accomplish many deeds as she desires to accomplish them.