Copernicus expressed his ingenious conviction about the revolu tion of the earth around the sun in the form of plausible hypothesis; but the simplicity of his formulation would not correspond to the radicality of the content. It was one of those vigorous ideas, almost with one's own life, with which one can be in agreement or in disconformity, but never indifferent.

In the philosophical field, the Kantian revolution is like that not only because it purports to be the inversion of the previous thought, but also because after the Dissertatio of 1770, philosophers have not been able to stop considering it and taking position before it.

In contemporary philosophy, Kantism still leaves a sufficient mark, and its consequences and influences are so important that we can affirm that in the philosophical realm, we are still living in a Kantian atmosphere.

Nevertheless the force of the philosopher of K nigsberg is based on the depth and importance of the questions which he asks than on the answers that he offers. The problems he poses are truly basic topics.

How are the sciences possible? With this question, Kant initi ated his investigation on the critical problem. The question is highly interesting and Kant formulates it to perfection. In the first place, it is perfectly legitimate, since it asks for the foundation of the sciences. In the second place, it is even obligatory for all the philosophers who are not satisfied with describing what is given, but try to reach its expla nation.

The situation would be different if he asked whether the sciences were possible. Doing that would incur in the clear illegitimacy of put ting in doubt the very existence of the sciences, which by itself is evident: "as these sciences are really given, one can ask about them: how are they possible? Since they have to be possible as it is demon strated by their reality"[1]

Kant examines the constitutive elements of what he considers sciences in order to isolate the essential ones from the accidental as pects. These elements will make the sciences possible. Before any-thing else, he observes that the scientific propositions are always universal and necessary, or - with his words - synthetic a priori judge ments.

For the German philosopher, the constituted sciences are Mathematics and Physics; but not Metaphysics. The motive of this discrimination is the success of the former and the failure of the latter in provoking the unanimous consent of those who profess them. To elevate Metaphysics to the rank of the mentioned sciences is an ethically praiseworthy try, although it is debatable insofar as its validity is concerned. The previous question is now posed in these words: Is Metaphysics possible as science?

It is well-known that the historical knowledge of the philosopher of K nigsberg is quite scarce. It does not go beyond Leibnizian rationalism - impoverished and spread by Wolff -, the empiricism of Hume and Newtonian physics. This could make us think that the problems aroused by Kant are similar to those which bothered Leibniz. The comparison of both authors shows effectively that the Kantian doctrine is not anything but a probing into the problems posed by his predecessor and an answer to those questions which the latter has left open. For example, the Kantian question: "How are the sciences (synthetic a priori judgements) possible?" refers to the Leibnizian problem: "How are the universal and necessary truths possible?" Notwithstanding, one particular point separates them: these truths be long, according to Leibniz, as much to Mathematics, Physics, Metaphysics as to morals. Both authors have then a common concern: that of discovering the foundation of Metaphysics. However, in Leibniz the Kantian prejudice of not considering Metaphysics as science is absent.

It can be said, without fear of exaggeration, that the Kantian solution is the consequence - certainly not wanted by its author - of the Leibnizian solution brought to its extreme. Perhaps we find ourselves before one of those sporadic cases in which the maxim enunciated bravely by Kant is fulfilled: "Any philosopher understands his prede cessors better than they themselves". This is reflected with particular clarity in determinate questions.

For Professor Verneaux, in the question of the origin of knowl edge, "Kant follows Leibniz purely and simply. He makes his own, under the new name of 'originating acquisition', the theory of the virtual innatism of the ideas."[2]

A scholar of Leibniz, Tonelli, suggests that "the Kantian revolu tion took as one of its central characteristics the rejection of the sensibility as the only source of knowledge. It is then easy to infer that Kant's reading of the New Essay Concerning Human Understanding (written by Leibniz) could be one of the elements which pushed him to adopt his new solution"[3]

Entering into the sphere of the probable that the reading of the New Essays has contributed in a great way to waken up the dogmatic dream of the creator of transcendental idealism, it can seem that this affirmation is adventurous; but from the chronological point of view, it does not lack foundation. Written in 1703-1705, the New Essays were not published until 1765, in the Raspe edition. The philosophical works that appeared during the successive years after 1765 showed that their authors did not understand with in depth the Leibnizian doctrine. Only Kant understood if fully. And the Dissertatio was given birth in 1770. With this, one does not pretend to affirm that Leibnizian innatism is Kant's only source of influence. The innatism of Crusius also plays an important role. Although Kant did not accept at first moment this moderate innatism, the knowledge of this doctrine could have called his attention by its analogy with that of Leibniz. The combined influence of both could be an important element in the famous philosophical revolution of 1770.[4]

The questions formulated by Leibniz and Kant do not constitute an absolute novelty. They are present in the previous philosophical systems; they were posed already by Plato, four centuries before Christ, in this form: "Why the universal and necessary truths are". A question which for him gives rise to all intellectual development.

The Platonic answer - the reminiscence - has great influence on the innate ideas of Leibniz. According to the doctrine of the reminis cence, the universal and necessary truths are in the soul in an uncon scious way even before its earthly existence. These truths remain hidden until they become conscious in a determinate moment by a series of perceptions which unleash in the soul an activity of comparison, combination and conclusion. Therefore, these truths are no more than remembrances of something forgotten, and their univer sality and necessity are precisely founded on their independence from experience.

St Augustine of Hippo, although influenced by Plato, could not accept the preexistence of the soul and rejects therefore the doctrine of the reminiscence, but he is aware of the fact that the sensible knowl edge cannot give origin to the universal and necessary truths, because the object of the first ones are the changeable realities. The Bishop of Hippo proposes to us then his famous solution: the divine illumination. The soul finds or recognizes in itself the universal and necessary truths because God is its interior Master. More intimate to It than its own intimity, the soul consults with the immutable Truth the knowledge which it acquires, and in It, it finds the scientific truths. In the same way as the sun illuminates the corporeal things, God is the source of the spiritual light which makes the reason understand the scientific truths. If the sun is the source of light, God is the source of truth. It is important to take note that St Augustine has recourse to the divinity only to justify the universality and necessity of the truths, but not to obtain the content. He avoids in this way the danger of incurring in a material innatism, that is to say, an innatism of mental content.

This question also called the attention of the Arab philosophers, among them, Avicenna. Influenced by the neo-platonists and Greek commentators of Aristotle, he affirmed - with a doctrine in conformity with that of Plato - that the One, First Principle, creates the First Intel ligence from which the rest proceeds by successive emanations, the last one being a Separated Agent Intellect common to all men. This Agent Intellect is the dator formarum, that is to say, the one who gives the form to the material beings and the knowledge of them in men. In this way, the universality and necessity of the truths are justified.[5]

In the opposite direction, we find the Aristotelic - Thomistic thinkers, who grant man the power which the Platonic line places out side of him. It is enough for us to recall briefly here the position of St Thomas of Aquinas who, following Aristotle, sustains that each man has his own agent intellect. It corresponds to it to justify the universal ity and necessity of the truths thanks to its capacity to abstract - and therefore to educe - the essences of the things starting from particular knowledge proceeding from the senses.

The current of thought defending the existence of universal and necessary truths are followed by Ockhamist nominalism which denies them stricto sensu. Ockham centers his attention in the particular beings, since for him there is no more reality than the singular or individual, as experience attests it. Consequently, there is no general knowledge. Nevertheless the experience itself seems to indicate that there are terms which designate general concepts. Ockham does not see in this more than the consequence of the limited human knowledge, which does not distinguish various objects among themselves. In principle, we should designate each thing or each real fact with a different word, since a common nature does not exist. In practice, because of economy of words, we put a multitude of similar things or facts under a same term; but being conscious of the fact that that "general" word only has extension but no comprehension.

The nominalist doctrine was later on adopted in its fullness by the empiricists like Locke, Hume, etc. Locke, for example, was one of those who attacked most strongly the doctrine of innate ideas, above all in his work Essay Concerning Human Understanding.

As a reaction against the empiricism of Locke, Leibniz wrote the Nouveaux essais sur l'entendement humain answering point by point the Essay of the English. For Leibniz, the existence of the universal and necessary truths is something evident. In order to solve the ques tion of how they are possible, he has recourse to innatism because the truths in question cannot come from the things themselves since expe-rience only gives us particular and contingent knowledge. Neither does it seem to him plausible that there be a continuous divine illumi nation. The Leibnizian solution, as he himself admits, is very much influenced by Platonism, although he declares that he is not in total agreement with the theory of the reminiscence.

Innatism, as a solution to the critical problem, corresponds to the psychological point of view. Nevertheless, we do not lack the corre sponding solution in a transcendental posture: the Kantian apriorism.

The doctrine of Kant sustains principally that transcendental knowledge or a priori knowledge is that which deals with objects in general, different from the empirical objects, that is to say, that in which all the objects - real or possible - converge and have to converge. His thought is quite well-known and it is enough for our purpose to remember that the matter of thought is the sensation, which gives us chaotic, amorphous phenomena. These phenomena are elaborated or ordered in two levels: first in the sensible level by the a priori forms of this level (space and time); afterwards in the intellectual level by the twelve categories, which are also a priori forms. The universality and the necessity of the knowledge are justified by the aprioristic forms, which do not come from the experience. As we can expect, the Kantian apriorism leads us to the conclusion that we only know the thing-in-me but we do not know the thing-in-itself because the form is given by the mind and it is not drawn from the thing in the reality.

Finally comes Hegel who introduces the absolute idealism which denies totally the existence of the external reality. For him, the only real things are the ideas in the human mind. The external reality is nothing more than a projection of the ideas in our mind. In this way, he converts the human mind into the creator of the things in the reality.

This brief historical panorama indicates that the problem of the universal is something perennial. The only correct solution is the one which can maintain the proper connection between the sense knowl edge and the intellectual knowledge without falling into the extremes.

The nominalists and empiricists on one hand are correct in maintaining that the only source of our knowledge is reality, our expe rience. Nevertheless, they commit the error of stopping our knowledge in the sensible level by denying the existence of universal truths. The innatists and idealists on the other hand are correct in distinguishing and accepting the jump between the sense knowledge and the universal and necessary truths; however they fall into the mistake of driving a wedge between them by claiming that the human mind is not a tabula rasa but rather it has inborn knowledge which does not come from the senses.

From here, we can see that the only correct solution to solve the critical question (How are the universal and necessary truths possible?) is the Aristotelic solution, maintained also by St Thomas of Aquinas, which affirms that each human mind has the capacity to abstract from the sensible data the essences of things in the reality; in this way, what we know is always the real nature of things in the reality (the things-in-themselves, not the things-in-me) but at the same time they do not remain in the particular level thanks to the power of the mind to abstract, to leave behind the sensible and keep only the intelligible. The Aristotelic-Thomistic solution is the only one which fulfills at the same time two essential goals: maintaining the distance between sense knowledge and the universal and necessary truths but without cutting the connection between them. That distance is important because thanks to it men are distinguished from the irrational beings, and that connection is important because it is the only natural way by which the truth of the universal and necessary knowledge can be saved.

As a conclusion we can say that the Aristotelic-Thomistic solu tion is the correct solution to the critical problem (the problem of the universal) because it is the solution which respects the true nature of man, a creature who does not only have a material body but also a spiritual soul; whereas the error of empiricism is to degrade man to the level of mere animal (i.e., without spiritual soul) and the mistake of idealism is to raise man to the level of God (i.e., forgetting his condi tion as a creature).

[1]KANT I., Cr tica de la razon pura, Vol.I, Trad. by MORENTE M.G. (Madrid: Liber a General de Victoriano Su rez 1928) 99.

[2]VERNEAUX R., Cr tica de la "Cr tica de la razon pura" (Madrid: Ed. Rialp 1978) 155.

[3]TONELLI G., Leibniz on Innate Ideas and the Early Reactions to the Publication of the Nouveaux Essais (1765) in J. Hist. Philoso 1974 (12) 437.

[4]Cf. Idem, 453.

[5]For more details, see HERNANDEZ M.C., Historia del pensamiento en el mundo isla mico, Vol.2 (Madrid: Ed. Alianza 1981) 193s..