We must acknowledge that the distinction between a priori and a posteriori raises many difficulties for an understanding of Hegel’s philosophy of nature. Some interpreters have contended that the a priori character of this philosophy makes it completely senseless in that it claims the legitimacy to replace empirical research of science with the pure logical necessity of thought or concepts.
Indeed, it might seem that once you claim the a priori character of your philosophy, any rational stance concerning scientific research is removed. How could the idea of the fallibility of science and, thus, of human knowledge be saved if you claim that this knowledge has a necessary character, implying that it is given once and for all?
Those who argue in this way (among them such famous thinkers as Karl Popper) forget two things: first that Hegel lived in a time when the idea of the fallibility of science was completely unintelligible. We must recall that, ultimately, his philosophy of nature was grounded on the Kantian philosophical premise that philosophy must offer the rational basis for natural science.
However, according to Kant and all his early followers, the latter proved to be the real knowledge of nature, a medium in which nature finally unveiled itself once and for all. Newtonian science was not a model of knowledge, one among many, as we think today, but it was the expression of the ultimate and highest manifestation of human reason.
This science was the expression of human reason’s success in overcoming any arbitrary character of human knowledge and was considered to present us with the final way of being of nature. (Only if you want to criticize Hegel in the eyes of those who claim that his ideas and philosophy are true eternally, beyond his epoch, and contain everlasting truths, might you be legitimate in your critique, which is the case, to some extent with Popper.)
The second thing forgotten by Hegel’s critics is that the distinction between a priori and a posteriori and the procedure of deduction of the concepts of the philosophy of nature has nothing to do with that widespread prejudice that, in Hegel’s philosophy, you can ‘deduce’ real knowledge from pure rational principles, as if Hegel ever maintained that he could derive or deduce the Newtonian law of gravitational attraction from the principle of sufficient reason or from the principle of identity.
In Hegel, as in Kant, ‘deduction’ has not the meaning it has in logic, where you ‘deduce’ the conclusion from its premises, as in classic syllogisms. Deduction means here to show what makes intelligible a certain concept that our knowledge already uses. It does not mean producing that concept, as happens in a syllogism, where the conclusion is produced logically with necessity from the premise.
Scientific knowledge has a large empirical content, that is to say, content acquired through observation. And the latter is always a posteriori and not a priori. However, science, as Kant rightly argued, is not a collection of empirical propositions but of necessary propositions, which means that those empirical observations are not taken in their empirical character, but in their a priori – that is to say, necessary and universal – character.
What is empirically observed, once integrated into science, becomes a moment, a sample, an individual case of the universal law that science enounces in its theory.
Science and scientists make a lot of empirical observations. However, not all of them become part of science, i.e., of what is sometimes called mainstream science. Some of those observations remain oddities for a very long time because the theory of science cannot integrate them into its body.
How does this integration take place? Through the development of science, that is to say, through the development of the theoretical part of science. This part is a collection of principles, theorems, definitions, demonstrations, etc., which are all universal propositions, stating something about all the cases of the same type of reality.
An empirical observation is the result of a measurement. However, the science of nature requires this result to be mathematically derived from the theoretical part of science. If scientists do not manage to offer a mathematical demonstration of that result, the latter remains an oddity until they manage to produce that demonstration.
Thus, in a certain sense, one could say that scientific knowledge produces its content not through observation but through logic, by deriving or deducing empirical knowledge from its theoretical part. There is no science of nature that operates differently.
However, it is a stupidity to think that the concrete, individual case can ever be produced only through that deduction. We, as humans, cannot anticipate something we do not know, except if we think of it as a particular case of universal law we already know.
When Columbus anticipated that by traveling toward the west, he would reach India, he based his anticipation on the representation that the earth was round. When Newton predicted the motion of planets, he could do this because he considered them as particular cases of the universal model of motion that he stated as a complex of principles of his theory.
But all these predictions needed concrete, individual cases to be observed previously and then a brilliant mind to conceive of a theoretical model in which such cases could be deduced logically and mathematically from that model.
The next part of this article can be read here.