The eternity of things in themselves or in God must also confound our brief duration. The fixed and constant immobility of Nature in comparison with the continual changes which take place in us must have the same effect.
And what completes our inability to know things is that they are in their essence simple, whereas we are composed of two opposite natures differing in kind, soul and body. For it is impossible that our reasoning part should be other than spiritual; and should any allege that we are simply material, this would far more exclude us from the knowledge of things, since it is an inconceivable paradox to affirm that matter can know itself, and it is not possible for us to know how it should know itself.
So, were we simply material, we could know nothing whatever, and if we are composed of spirit and matter we cannot perfectly know what is simple, whether it be spiritual or material. For how should we know matter distinctly, since our being, which acts on this knowledge, is partly spiritual, and how should we know spiritual substances clearly since we have a body which weights us, and drags us down to earth.
Moreover what completes our inability is the simplicity of things compared with our double and complex nature. To dispute this point were an invincible absurdity, for it is as absurd as impious to deny that man is composed of two parts, differing in their nature, soul and body. This renders us unable to know all things; for if this complexity be denied, and it be asserted that we are entirely material, it is plain that matter is incapable of knowing matter. Nothing is more impossible than this.
Let us conceive then that this mixture of spirit and clay throws us out of proportion....
Hence it comes that almost all philosophers have confounded different ideas, and speak of material things in spiritual phrase, and of spiritual things in material phrase. For they say boldly that bodies have a tendency to fall, that they seek after their centre, that they fly from destruction, that they fear a void, that they have inclinations, sympathies, antipathies; and all of these are spiritual qualities. Again, in speaking of spirits, they conceive of them as in a given spot, or as moving from place to place; qualities which belong to matter alone.
Instead of receiving the ideas of these things simply, we colour them with our own qualities, and stamp with our complex being all the simple things which we contemplate.
Who would not think, when we declare that all that is consists of mind and matter, that we really understood this combination? Yet it is the one thing we least understand. Man is to himself the most marvellous object in Nature, for he cannot conceive what matter is, still less what is mind, and less than all how a material body should be united to a mind. This is the crown of all his difficulties, yet it is his very being: Modus quo corporibus adhæret spiritus comprehendi ab homine non potest et hoc tamen homo est.
These are some of the causes which render man so totally unable to know nature. For nature has a twofold infinity, he is finite and limited. Nature is permanent, and continues in one stay; he is fleeting and mortal. All things fail and change each instant, he sees them only as they pass, they have their beginning and end, he conceives neither the one nor the other. They are simple, he is composed of two different natures. And to complete the proof of our weakness, I will finish by this reflection on our natural condition. In a word, to complete the proof of our weakness, I will end with these two considerations....
The nature of man may be considered in two ways, one according to its end, and then it is great and incomparable; the other according to popular opinion, as we judge of the nature of a horse or a dog, by popular opinion which discerns in it the power of speed, et animum arcendi; and then man is abject and vile. These are the two ways which make us judge of it so differently and which cause such disputes among philosophers.