What subjects must we study?

⁶⁶

The power of mechanical arts changes bodies materially by composition or separation. It perverts human understanding by inducing it to suppose that something similar takes place in the universal nature of things.

Hence the fiction of elements,[39] and their co-operation in forming natural bodies.[29]

When man reflects upon the entire liberty of nature, he meets with particular species of things, as animals, plants, minerals.

He is thence easily led to imagine that:

• nature has primary forms which she strives to produce
  • This hypothesis produced the doctrine of elementary properties.
• all variation in them comes from some error while she was completing her work, or the collision or metamorphosis of different species.
  • This produced the doctrine of occult properties and specific powers

Both lead to trifling courses of reflection, in which the mind acquiesces, and is thus diverted from more important subjects.

But physicians exercise a much more useful labor in the consideration of the secondary qualities of things, and the operations of attraction, repulsion, attenuation, inspissation, dilatation, astringency, separation, maturation, etc.

They would do still more if they would not corrupt these proper observations by the two systems I have alluded to, of elementary qualities and specific powers, by which they either reduce the secondary to first qualities, and their subtile and immeasurable[40] composition, or at any rate neglect to advance by greater and more diligent observation to the third and fourth qualities, thus terminating their contemplation prematurely.

Nor are these powers (or the like) to be investigated only among the medicines for the human body, but also in all changes of other natural bodies.

A greater evil arises from the contemplation and investigation of the stationary principles of things from which, than of the active by which things themselves are created.

For the former only serve for discussion, the latter for practice. Nor is any value to be set on those common differences of motion which are observed in the received system of natural philosophy, as generation, corruption, augmentation, diminution, alteration, and translation.

For this is their meaning: if a body, unchanged in other respects, is moved from its place, this is translation; if the place and species be given, but the quantity changed, it is alteration; but if, from such a change, the mass and quantity of the body do not continue the same, this is the motion of augmentation and diminution; if the change be continued so as to vary the species and substance, and transfuse them to others, this is generation and corruption.

All this is merely popular, and by no means penetrates into nature; and these are but the measures and bounds of motion, and not different species of it; they merely suggest how far, and not how or whence.

For they exhibit neither the affections of bodies nor the process of their parts, but merely establish a division of that motion, which coarsely exhibits to the senses matter in its varied form.

Even when they wish to point out something relative to the causes of motion, and to establish a division of them, they most absurdly introduce natural and violent motion, which is also a popular notion,[41] since every violent motion is also in fact natural, that is to say, the external efficient puts nature in action in a different manner to that which she had previously employed.

But if, neglecting these, any one were, for instance, to observe that there is in bodies a tendency of adhesion, so as not to suffer the unity of nature to be completely separated or broken, and a vacuum[30] to be formed, or that they have a tendency to return to their natural dimensions or tension, so that, if compressed or extended within or beyond it, they immediately strive to recover themselves, and resume their former volume and extent; or that they have a tendency to congregate into masses with similar bodies—the dense, for instance, toward the circumference of the earth, the thin and rare toward that of the heavens. These and the like are true physical genera of motions, but the others are clearly logical and scholastic, as appears plainly from a comparison of the two.

Another considerable evil is, that men in their systems and contemplations bestow their labor upon the investigation and discussion of the principles of things and the extreme limits of nature, although all utility and means of action consist in the intermediate objects. Hence men cease not to abstract nature till they arrive at potential and shapeless matter,[31] and still persist in their dissection, till[42] they arrive at atoms; and yet were all this true, it would be of little use to advance man’s estate.

⁶⁷ The understanding must also be cautioned against the intemperance of systems, so far as regards its giving or withholding its assent; for such intemperance appears to fix and perpetuate idols, so as to leave no means of removing them.

These excesses are of two kinds. The first is seen in those who decide hastily, and render the sciences positive and dictatorial. The other in those who have introduced scepticism, and vague unbounded inquiry. The former subdues, the latter enervates the understanding.

The Aristotelian philosophy destroyed other systems (just as the Ottomans[32] destroy their brethren) by its disputatious confutations.

• It decided on everything
• Aristotle himself asks questions at will, in order to settle them.
• In this way, everything is certain and decided, a method now used by his successors.

The school of Plato disliked Protagoras, Hippias,[33] and others who were ashamed of appearing not[43] to doubt any subject.

• For them, Plato introduced skepticism, initially as a joke and irony to them
• But the new academy dogmatized in their scepticism, and held it as their tenet.

This method of skepticism is more honest than arbitrary decision.

• Its followers allege that they do not confound all inquiry, like Pyrrho and his disciples
• They say that they hold doctrines which they can follow as probable, even if they cannot maintain them to be true.

Yet when the human mind has once despaired of discovering truth, everything begins to languish.

Hence, men revert into:

• pleasant discussions
• wandering over subjects instead of sustaining any rigorous investigation.

But we should deny the authority of the human senses and understanding, however weak. Instead, we furnish them with assistance.