Material objects do not send forth species resembling them

The most common opinion is that of the Peripatetics.

They claim that:

• external objects send forth species resembling them
• these species are carried by the external senses to the common sense

They call these species impressed because objects imprint them on the external senses.

These impressed species are:

• material and sensible
• rendered intelligible by the agent or active intellect
• fit to be received into the patient intellect

These species, thus spiritualized, are called expressed species because they are expressed from the impressed ones; and it is by these that the patient intellect knows all material things.

We shall not pause to explain these fine things at greater length, nor the various ways in which different philosophers conceive them. For although they do not agree on the number of faculties they attribute to the inner sense and to the understanding—and indeed many of them strongly doubt whether they need an agent intellect to know sensible objects—they nevertheless almost all agree that external objects send forth species or images resembling them.

It is only on this foundation that they multiply their faculties and defend their agent intellect. So, since this foundation has no solidity, as will be shown, it is not necessary to pause further to overturn everything that has been built upon it.

I assert that it is not plausible that objects send forth images or species resembling them. Here are some reasons. The first is drawn from the impenetrability of bodies. All objects—like the sun, the stars, and all those near our eyes—cannot send forth species of a nature different from their own.

This is why philosophers ordinarily say that these species are coarse and material, in contrast to expressed species, which are spiritualized. These impressed species of objects are therefore little bodies. Consequently, they cannot penetrate one another, nor can they fill all the spaces from the earth to the sky, which would have to be completely filled by them. From this it is easy to conclude that they would have to crush and break one another, some going one way and others another, and thus they could not make objects visible.

Moreover, from a single place or a single point one can see a very great number of objects in the sky and on the earth. Therefore, the species of all these bodies would have to be reducible to a single point. But since they are extended, they are impenetrable. Therefore…

But not only can one see a very great number of very large and vast objects from a single point; there is no point in all those great spaces of the world from which one could not discover an almost infinite number of objects—and even objects as large as the sun, the moon, and the heavens. There is therefore no point [12] in the whole world where the species of all these things would not have to meet; which is contrary to all appearance of truth.

The second reason is drawn from the change that occurs in the species. It is certain that the closer an object is, the larger its species must be, since we see the object larger. Now, one does not see what can make this species diminish, nor what becomes of the parts that composed it when it was larger. But what is even more difficult to conceive according to their view is that if one looks at this object with magnifying glasses or a microscope, the species suddenly becomes five or six hundred times larger than it was before; for one sees even less by what parts it can increase so greatly in an instant.

The third reason is that when one looks at a perfect cube, all the species of its sides are unequal, and yet one still sees all its sides equally square. Likewise, when one considers ovals and parallelograms in a painting—which can only send species of similar shape—one nevertheless sees only circles and squares. This clearly shows that it is not necessary for the object one looks at to produce, in order for it to be seen, species resembling it.

Finally, one cannot conceive how it can happen that a body which does not noticeably diminish always sends forth species from itself in all directions, continually filling very large spaces all around with them, and that with an inconceivable speed. For when a hidden object is uncovered, it can be seen from several million leagues away and from all sides. And what seems even stranger is that bodies which have much activity, like air and some others, do not have the force to push out images resembling themselves; while the coarsest bodies, which have the least activity—like earth, stones, and almost all hard bodies—do.

But we do not wish to pause further to relate all the reasons against this opinion, because it would never be finished; the slightest effort of the mind furnishes such a great number that one cannot exhaust them. Those we have just related are sufficient, and they were not even necessary after what has been said on this subject in the first book, when the errors of the senses were explained. But so many philosophers are attached to this opinion that it was thought necessary to say something about it to induce them to reflect on their thoughts.