Part 14 (1/2)
_The Three Kinds of Knowledge_
From what has been already said, it clearly appears that we perceive many things and form universal ideas:
1. From individual things, represented by the senses to us in a mutilated and confused manner, and without order to the intellect. These perceptions I have therefore been in the habit of calling knowledge from vague experience.
2. From signs; as, for example, when we hear or read certain words, we recollect things and form certain ideas of them similar to them, through which ideas we imagine things. These two ways of looking at things I shall hereafter call knowledge of the first kind, opinion or imagination.
3. From our possessing common notions and adequate ideas of the properties of things. This I shall call reason and knowledge of the second kind.
Besides these two kinds of knowledge, there is a third, as I shall hereafter show, which we shall call intuitive science. This kind of knowing advances from an adequate idea of the formal essence of certain attributes of G.o.d to the adequate knowledge of the essence of things.
All this I will explain by one example. Let there be three numbers given through which it is required to discover a fourth which shall be to the third as the second is to the first. A merchant does not hesitate to multiply the second and third together and divide the product by the first, either because he has not yet forgotten the things which he heard without any demonstration from his school-master, or because he has seen the truth of the rule with the more simple numbers, or because from the 19th Prop. in the 7th book of Euclid he understands the common property of all proportionals.
But with the simplest numbers there is no need of all this. If the numbers 1, 2, 3, for instance, be given, every one can see that the fourth proportional is 6 much more clearly than by any demonstration, because from the ratio in which we see by one intuition that the first stands to the second we conclude the fourth.
To knowledge of the first kind we have said that all those ideas belong which are inadequate and confused, and, therefore, this knowledge alone is the cause of falsity. Moreover, to knowledge of the second and third kind we have said that those ideas belong which are adequate, and therefore this knowledge is necessarily true.
It is the knowledge of the second and third, and not that of the first kind, which teaches us to distinguish the true from the false. For he who knows how to distinguish between the true and the false must have an adequate idea of the true and the false, that is to say, he must know the true and the false by the second or third kind of knowledge.
_Reason and Imagination_
It is in the nature of reason to perceive things truly, that is to say, as they are in themselves, that is to say, not as contingent but as necessary.
Hence it follows that it is through the imagination alone that we look upon things as contingent both with reference to the past and the future.
How this happens I will explain in a few words. We have shown above that unless causes occur preventing the present existence of things, the mind always imagines them present before it, even if they do not exist.
Again, we have shown that if the human body has once been simultaneously affected by two external bodies, whenever the mind afterwards imagines one it will immediately remember the other; that is to say, it will look upon both as present before it, unless causes occur which prevent the present existence of the things. No one doubts, too, that we imagine time because we imagine some bodies to move with a velocity less, or greater than, or equal to that of others.
Let us therefore suppose a boy who yesterday, for the first time, in the morning saw Peter, at midday Paul, in the evening Simeon, and to-day in the morning again sees Peter. It is plain that as soon as he sees the morning light he will imagine the sun pa.s.sing through the same part of the sky as on the day preceding; that is to say, he will imagine the whole day, and at the same time Peter will be connected in his imagination with the morning, Paul with midday, and Simeon with the evening. In the morning, therefore, the existence of Paul and Simeon will be imagined in relation to future time, while in the evening, if the boy should see Simeon, he will refer Peter and Paul to the past, since they will be connected with the past in his imagination. This process will be constant in proportion to the regularity with which he sees Peter, Paul, and Simeon in this order. If it should by some means happen that on some other evening, in the place of Simeon, he should see James, on the following morning he will connect in his imagination with the evening at one time Simeon and at another James, but not both together. For he is supposed to have seen one and then the other in the evening, but not both together. His imagination will therefore fluctuate, and he will connect with a future evening first one and then the other; that is to say, he will consider neither as certain, but both as a contingency in the future.
This fluctuation of the imagination will take place in the same way if the imagination is dealing with things which we contemplate in the same way with reference to past or present time, and consequently we imagine things related to time past, present, or future as contingent.
_Sub Specie aeternitatis_
It is of the nature of reason to consider things as necessary and not as contingent. This necessity of things it perceives truly, that is to say, as it is in itself. But this necessity of things is the necessity itself of the eternal nature of G.o.d. Therefore it is of the nature of reason to consider things under this form of eternity. Moreover, the foundations of reason are notions which explain those things which are common to all, and these things explain the essence of no individual thing, and must therefore be conceived without any relation to time, but under a certain form of eternity.
_The Limits of Human Knowledge_
I
The parts composing the human body pertain to the essence of the body itself only in so far as they communicate their motions to one another by some certain method, and not in so far as they can be considered as individuals without relation to the human body. For the parts of the human body are individuals, composite to a high degree, parts of which can be separated from the human body and communicate their motions to other bodies in another way, although the nature and form of the human body itself is closely preserved. Therefore the idea or knowledge of each part will be in G.o.d in so far as He is considered as affected by another idea of an individual thing, which individual thing is prior to the part itself in the order of Nature. The same thing may be said of each part of the individual itself composing the human body, and therefore the knowledge of each part composing the human body exists in G.o.d in so far as He is affected by a number of ideas of things, and not in so far as He has the idea of the human body only; that is to say, the idea which const.i.tutes the nature of the human mind; and therefore the human mind does not involve an adequate knowledge of the parts composing the human body.
We have shown that the idea of a modification of the human body involves the nature of an external body so far as the external body determines the human body in some certain manner. But in so far as the external body is an individual which is not related to the human body, its idea or knowledge is in G.o.d, in so far as He is considered as affected by the idea of another thing, which idea is prior by nature to the external body itself. Therefore the adequate knowledge of an external body is not in G.o.d in so far as He has the idea of the modification of the human body, or, in other words, the idea of the modification of the human body does not involve an adequate knowledge of an external body.
When the human mind through the ideas of the modifications of its body contemplates external bodies, we say that it then imagines, nor can the mind in any other way imagine external bodies as actually existing.