In his short treatise On Being and Essence, Thomas Aquinas says “A slight error eventually grows to vast proportions, according to the Philosopher.” The philosopher referred to is Aristotle, and the quote referred to is found in De Caelo, book I, “So it has been and so it must be; since the least initial deviation from the truth is multiplied later a thousandfold...The reason is that a principle is great rather in power than in extent.” This would seem to be true regardless of the branch of studies. If we make an error in the principles of our philosophy, then, though we may stumble upon some truths, our system, as a whole, will be unstable and erroneous.
How then do we make sure that we are starting from the right principles? Socrates, in the Phaedo, offered his method of finding truth, “However, I started in this manner: taking as my hypothesis in each case the theory that seemed to me the most compelling, I would consider as true, about cause and everything else, whatever agreed with this, and as untrue whatever did not so agree.” Now this method worked fine for Socrates who, being one of the first philosophers, could not study a history of philosophy which spanned for thousands of years before him. This is important because he could not observe, through thousands of years, what had happened when a philosopher chose a certain principle as his foundation. Now, philosophy is, in general, not an experimental science, which is to say, if we want to discover what the principle of philosophy is, we cannot perform experiments in a laboratory. However, we, unlike Socrates, now have thousands of years of the history of thought to observe. We can now look at the great and not so great philosophers of the past in order to see which philosophical principles lead which conclusions. Étienne Gilson, in Thomistic Papers V, said, “But we can observe the history of philosophy and appeal to observations with a view to assuring ourselves, by seeing them emerge in fact from a principle, that certain knowledge is in fact contained in it. Then the proof that x by right implies a, b, c, d is that in fact, in the course of time, and sometimes after an interval of centuries, a, b, c, d have finally emerged from it.”
We no longer need, necessarily, to ask the question, if I posit X as a principle, what will happen? Will X lead to the truth? Gilson, in the same article, says, “To the abstract question: what happens if we posit x as a principle? The experiment facilitates the answer. By calling upon the data of history we can see concretely what in fact has happened.”
Now, we should not attribute all of the consequences of any given principle to the philosopher who posited the principle, however, this does not restrain us from proclaiming, with certainty, that given X, necessarily (relative to the addition of, or removal of, some other principle that may have been present in the original philosophers theory) a, b, c, d, et al.
We now see the immediate importance of studying the history of philosophy. We must study history so as not to repeat the errors of our ancestors. In fact, as Gilson says, the experiments of philosophy are carried out by the discourse of philosophers throughout the centuries. The laboratory of the philosopher is the study of the history of philosophy. When we study the history of philosophy, we should be seeking, not simply that which seem interesting, or that which agrees with our general philosophical stance, but the consequences of ideas. We should be seeking the principles of the theories of the philosophers, and following them to their conclusions. We are seeking truth, but truth will not be found if we do not start from the true principle.
One of the most interesting examples, that we find in the history of philosophy, of how the theories of one philosopher engendered, not just one school, but numerous conflicting schools, is that of Descartes. He lived in a time when apologetics was the concern of the day. The Catholic Church was struggling, on many different fronts, against the birth of Protestantism, the influences of other religions and the ever-growing Atheistic influences. Descartes, in this atmosphere, sought to break with scholastic philosophy, and, in defence of the perennial Christian faith, to build a philosophical system which was unassailable, and indubitable. His philosophy, so long as we retain his own view of his philosophy, is properly realistic. He seeks to prove the existence of a real, mind-exterior, world. However, from the principles which he lays down, sprang almost all of the modern theories of philosophy by either the rejection or modification of Descartes’ principles. Maritain puts it quite well, “And thus although his intentions may have been realist, in actual fact he has propounded the problem and introduced that principle of modern idealism.”
It is, therefore, necessary to study the history of philosophy so as to understand how different principles lead to varying conclusions and so, to keep ourselves from making the same errors. As I noted at the beginning, “A slight error eventually grows to vast proportions, according to the Philosopher.”
Thomas Aquinas, On Being and Essence, trans. Armand Maurer, 2nd ed. (Toronto, ON: PIMS, 1968), 28.
Aristotle, “On the Heavens 271b9-13,” in The Basic Works of Aristotle, ed. Richard McKeon, trans. J. L. Stocks (New York, NY: Random House, 1941), 404.
Socrates, Phaedo 100a, trans. G. M. A. Grube (Indianapolis, IN: Hackett, 1977), 50.
Étienne Gilson, “Remarks on Experience in Metaphysics,” in Thomistic Papers, ed. Thomas A. Russman (Houston, TX: Center for Thomistic Studies, 1990), 5: 43.
True Philosophers are seeking the truth. This is the sign of a truly Christian philosophy - the pursuit of truth. As Jacques Maritain says, “Nevertheless a philosophy must be nothing but true; then and then only is it really Christian.” (Jacques Maritain, “The Revelation of Science,” in The Dream of Descartes, trans. Mabelle L. Andison (New York, NY: Philosophical Library, 1944), 38.)
Quite frequently a philosopher posits a number of principles that, together, give the desired conclusion. However, his followers do not necessarily accept all of the principles. So, by the removal, or addition, of any given principle the original philosophers’ theory will be transformed.
There seems to be a distinction between absolute and relative necessity. Absolute necessity is that which describes the situation when X follows, regardless of other principles or circumstances, necessarily from Y. Most people understand immediately what absolute necessity is, it can be represented by the logical formula X→Y. Relative necessity is the description of the situation when X follows necessarily, based upon other principles or circumstances, from Y. In other words, if I want to go from Quebec City to Toronto, and arrive before supper, then I only have a couple choices. If there were no restraints at all, then I could walk, ride a bike or horse, drive my car, take a bus or train, take a taxi, or fly, etc. However, if I have limited money, I have no car, and have a time delay then I may have to take plane. Another way of describing relative necessity would be to call it contingent necessity, because X follows from Y, contingent on a, b, c, d.
Maritain, 33. See also, Harry M. Bracken , Descartes: A Beginner’s Guide (Oxford: OneWorld, 2010), 2, 8, 12-3.
Cf. René Descartes, “Rules for the Direction of the Mind,” in The Philosophical Works of Descartes, trans. Elizabeth S. Haldane & G. R. T. Ross (1911; repr., Cambridge: Cambridge University Press, 1984), 1: 7. Note his attitude to scholastic philosophy, which was in many cases influenced by Aristotle, “From lack of having known this truth, or else, if there be those who have known it, from neglecting it, the greater part of those in later times who aspired to be philosophers have blindly followed Aristotle, so that frequently they have corrupted the sense of his writings, attributing diverse opinions to him which he would not recognise as his, were he to return to this world; and those have not followed him (amongst whom many of the best minds are to be found) have yet been imbued with his teaching in their youth, for it forms the sole teaching in the Schools; and these minds were so much occupied with this, that they were incapable of attaining to a knowledge of true Principles.” (René Descartes, “The Principles of Philosophy,” in The Philosophical Works of Descartes, trans. Elizabeth S. Haldane & G. R. T. Ross (1911; repr., Cambridge: Cambridge University Press, 1984), 1: 207.) Later on he adds, “On the other hand the controversies of the Schools, by insensibly making those who practise themselves in them more captious and self-sufficient, are possibly the chief causes of the heresies and dissensions which now exercise the world.” (Ibid., 1: 213).
René Descartes, “Meditations on First Philosophy,” in The Philosophical Works of Descartes, trans. Elizabeth S. Haldane & G. R. T. Ross (1911; repr., Cambridge: Cambridge University Press, 1984), 1:134, 138.