Hobbes says metaphors used in reasoning are folly but most of his arguments are analogies, or from definitions which he has defined in terms of his system. He begins by describing things from a physical mechanistic causation; but at some point he moves over to a mental causation as if they were the same thing.
Singly, the thoughts of man are representations or Appearances of some quality or other Accident of an object outside us. Which work on each of the senses and by that diversity produce a variety of Appearances.
The origin of all thoughts is Sense. Sense is caused by the object, it puts pressure on a sense organ (immediate-Taste and Touch, and mediate-Seeing, Hearing, Smelling), which is mediated by the way of nerves (and other strings) to the brain and heart where there is a counter-pressure. This seeming or fancy is sense. All qualities we call sensible are in the object that caused them and in us as diverse motions (for motion, produces nothing but motion). But their appearance to us is fancy, the same waking, that dreaming. And as pressing on the eye makes us fancy a light, so do the bodies we see, produce the same by their strong though unobserved action. For if the colors and sounds were in the objects, they couldn’t be severed from them as by glasses or echoes we see they are, because we know the object is in one place and its appearance in another. So that sense is nothing else than original fancy, caused by the motion or pressure upon our sense organs.
But the scholastics say for the cause of vision, the object seen, sends out a visible species, apparition, aspect, or a being seen, whereof the receiving in the eye is seeing. Likewise for hearing but the object sends out an audible species. And as well for understanding, the object sends out an intelligible species. I don’t say this to disapprove of the use of Universities because they do have a use in the Commonwealth but rather to amend in them certain things, like insignificant speech.
An object at rest will remain at rest, unless something else moves it (because nothing can change itself), no one doubts, but less assented to is an object in motion will remain in motion, unless something else stops it (for the same reason as the first). For men measure everything by themselves, and because men are tired after motion, they believe all objects to naturally move towards rest. Scholastics say “Heavy bodies fall downwards, out of an appetite to rest, and to conserve their nature in that place most proper for them.” Which is ascribing knowledge, which is more than man has, to inanimate objects.
Whatever hinders an object in motion must stop it in time and by degrees, not instantly, as in the case of waves continuing when the wind stops, and also when a man sees or dreams, for when the eye is shut, we still retain an image though more obscure. This is what the Latins call imagination, which is decaying sense, and is found in waking and sleeping.