Welcome to Episode One Hundred Twenty One of Lucretius Today. This is a podcast dedicated to the poet Lucretius, who wrote “On The Nature of Things,” the only complete presentation of Epicurean philosophy left to us from the ancient world. I am your host Cassius, and together with our panelists from the EpicureanFriends.com forum, we’ll walk you through the ancient Epicurean texts, and we’ll discuss how Epicurean philosophy can apply to you today. We encourage you to study Epicurus for yourself, and we suggest the best place to start is the book “Epicurus and His Philosophy” by Canadian professor Norman DeWitt. If you find the Epicurean worldview attractive, we invite you to join us in the study of Epicurus at EpicureanFriends.com, where you will find a discussion thread for each of our podcast episodes and many other topics. Today we continue our review of Epicurus’ letter to Herodotus, and we move further into fundamental physics of the atoms and we introduce the topic of the soul. Now let’s join Martin reading today’s text:
 Furthermore, in the infinite we must not speak of “up” or “down,” as though with reference to an absolute highest or lowest — and indeed we must say that, though it is possible to proceed to infinity in the direction above our heads from wherever we take our stand, the absolute highest point will never appear to us — nor yet can that which passes beneath the point thought of to infinity be at the same time both up and down in reference to the same thing: for it is impossible to think this. So that it is possible to consider as one single motion that which is thought of as the upward motion to infinity and as another the downward motion, even though that which passes from us into the regions above our heads arrives countless times at the feet of beings above and that which passes downwards from us at the head of beings below; for none the less the whole motions are thought of as opposed, the one to the other, to infinity.
 Moreover, the atoms must move with equal speed, when they are borne onwards through the void, nothing colliding with them. For neither will the heavy move more quickly than the small and light, when, that is, nothing meets them: nor again the small more quickly than the great, having their whole course uniform, when nothing collides with them either: nor is the motion upwards or sideways owing to blows quicker, nor again that downwards owing to their own weight. For as long as either of the two motions prevails, so long will it have a course as quick as thought, until something checks it either from outside or from its own weight counteracting the force of that which dealt the blow. Moreover, their passage through the void, when it takes place without meeting any bodies which might collide, accomplishes every comprehensible distance in an inconceivably short time. For it is collision and its absence which take the outward appearance of slowness and quickness.
 Moreover, it will be said that in compound bodies too one atom is faster than another, though as a matter of fact all are equal in speed: this will be said because even in the least period of continuous time all the atoms in aggregate bodies move towards one place, even though in moments of time perceptible only by thought they do not move towards one place but are constantly jostling one against another, until the continuity of their movement comes under the ken of sensation. For the addition of opinion with regard to the unseen, that the moments perceptible only by thought will also contain continuity of motion, is not true in such cases; for we must remember that it is what we observe with the senses or grasp with the mind by an apprehension that is true. Nor must it either be supposed that in moments perceptible only by thought the moving body too passes to the several places to which its component atoms move (for this too is unthinkable, and in that case, when it arrives all together in a sensible period of time from any point that may be in the infinite void, it would not be taking its departure from the place from which we apprehend its motion); for the motion of the whole body will be the outward expression of its internal collisions, even though up to the limits of perception we suppose the speed of its motion not to be retarded by collision. It is of advantage to grasp this first principle as well.
 Next, referring always to the sensations and the feelings, for in this way you will obtain the most trustworthy ground of belief, you must consider that the soul is a body of fine particles distributed throughout the whole structure, and most resembling wind with a certain admixture of heat, and in some respects like to one of these and in some to the other. There is also the part which is many degrees more advanced even than these in fineness of composition, and for this reason is more capable of feeling in harmony with the rest of the structure as well. Now all this is made manifest by the activities of the soul and the feelings and the readiness of its movements and its processes of thought and by what we lose at the moment of death.
 Further, you must grasp that the soul possesses the chief cause of sensation: yet it could not have acquired sensation, unless it were in some way enclosed by the rest of the structure. And this in its turn having afforded the soul this cause of sensation acquires itself too a share in this contingent capacity from the soul. Yet it does not acquire all the capacities which the soul possesses: and therefore when the soul is released from the body, the body no longer has sensation. For it never possessed this power in itself, but used to afford opportunity for it to another existence, brought into being at the same time with itself: and this existence, owing to the power now consummated within itself as a result of motion, used spontaneously to produce for itself the capacity of sensation and then to communicate it to the body as well, in virtue of its contact and correspondence of movement, as I have already said.
 Therefore, so long as the soul remains in the body, even though some other part of the body be lost, it will never lose sensation; nay more, whatever portions of the soul may perish too, when that which enclosed it is removed either in whole or in part, if the soul continues to exist at all, it will retain sensation. On the other hand the rest of the structure, though it continues to exist either as a whole or in part, does not retain sensation, if it has once lost that sum of atoms, however small it be, which together goes to produce the nature of the soul. Moreover, if the whole structure is dissolved, the soul is dispersed and no longer has the same powers nor performs its movements, so that it does not possess sensation either.
 For it is impossible to imagine it with sensation, if it is not in this organism and cannot effect these movements, when what encloses and surrounds it is no longer the same as the surroundings in which it now exists and performs these movements.