The following text is from a chapter called “Concerning Knowledge,” from the book Philosophy of the Understanding by Andres Bello. The book can be purchased from Amazon. The book was originally written in Spanish and published in 1881. The text was translated into English by Alan. You can read the Spanish side-by-side with the English on my bilingual website. (image on the left: portrait of Andres Bello by Raymond Monvoisin; image on the right: portrait of Immanuel Kant)
Ideas, then, that do not come directly from observation, come indirectly from it through the faculties that we have enumerated, aided, if you will, by certain instincts that, to me, are revealed in the natural fluidity of the imagination.
But forming an idea is not the same thing as reasoning. Forming an idea of a centaur or a hippogriff is not the same thing as affirming its existence.
It is incontestable that, in all our knowledge, a lot of reasoning is involved, and the most important kind is that which nascent experience has not been able to give us, and that which is limited to the observation of individual events.
When I connect certain olfactory sensations to the same cause that produces in me certain tactile sensations; when I connect, for example, the flower that I hold in my hand to the fragrance that my nose perceives, I am using strictly experimental reasoning. But even propositions of this type (individual propositions, the first source of experience), assume certain instincts that, when generalized, later become principles or fundamental laws that preside over all intelligent acts. Such is the principle of causality, which connects every phenomenon to a cause; such is the principle of substantiality, which does not allow me to conceive a quality or a change without a substrate, without a substance in which it exists; such is the principle of non-contradiction, by virtue of which I cannot conceive that a thing is, and is not, at the same time; such is the principle of sufficient reason, by virtue of which I conceive that, with respect to everything that is, there is a reason for it to be what it is and not something else.
There is a particular constitutive principle of that experience, consisting of generalized observations. When I observe that when I rub wax with a piece of wool, it acquires the property of attracting the lightweight bodies that are nearby, and having done this experiment with the same result several times, I reason that in all of them the rubbing of the wax and the wool has produced and will produce the same effect, I take a great step outside the limits of observation, because it is evident that I could not think so if I did not proceed on the principle of the stability of the laws of nature; on the principle that I have called empirical, not because it is so, but rather because on it is based the generalization of all empirical results, the metamorphosis of an observed phenomenal connection into a constant phenomenal connection, into a necessary phenomenal connection. My observations undoubtedly enable me to know, as far as they go, the stability of certain connections; to extend this beyond the present sphere and even beyond the possible sphere of my observations, and even beyond the observations of the whole human race, and even beyond the observations of all finite intelligences; to reason that it is always established, and that it is impossible for it to fail, is a place to which neither perception, nor memory, nor imagination can lead us, without the aid of a tendency or spontaneous instinct to reason thus; nature suggests this reasoning; our reason accepts it, and we reason with the empirical principle, making it not so much a premise as an assumption of all our reasoning regarding phenomena. We can formulate it like this: Given the cause, the effect necessarily follows; that is, given the precursor phenomenon, the second phenomenon necessarily occurs.
“A thing cannot be and not be at the same time.” This is the formula of a fundamental proposition that is called the principle of non-contradiction; this principle is not only superior to the reach of observation, but absolutely necessary for all reasoning, for all rationalizations, for all knowledge. Suppose for a moment that such a principle did not exist: Nothing could be proven, nothing could be rationalized, nothing could be known. The law of non-contradiction is evidently a universal, irresistible fundamental virtue, which not only does not admit of proof, but does not allow anything to be proven or admitted without it.