The opposition between natural and social sciences started in ancient Greece as a relationship between theoretical and practical sciences. This opposition was set for the first time by Aristotle while asserting his theory of soul and his methodology of science. Thus, different functions of soul are responsible for these two kinds of sciences and, similarly, there are two logical instruments for each science to discover their scientific truths. If theoretical sciences use the apodictical syllogism that concludes from necessary premises, the practical sciences make use of the dialectical syllogism that starts from probable premises. The theoretical/ practical opposition is mirrored at the methodological level through the pair of terms apodictic/ dialectic.
Keywords: Aristotelian theory of science, theoretical sciences, practical sciences, Aristotelian theory of soul, Aristotelian logic, apodictic, dialectic
Although disparate scientific knowledge existed before Greek civilization, science in its systematic form begins to spring with the sixth century on the territories of ancient Greece, the point that is also considered as the true beginnings of the philosophical research. Physical universe was the first object to which researchers have turned their attention to draw cosmological theories. The first who conceived such theories was the représentants of socalled School of Miletus in the early sixth century, whose main members were Thales, Anaximander and Anaximene. Although their theories about the genesis and evolution of the universe are considered the first authentic cosmologies, because of their explanations free of mythological elements, they initiated at the same time metaphysical explanation regarding the nature of the first principles. Thus physics and metaphysics entwine in their theories about universe without can draw a clear line of demarcation between scientific and philosophical explanations. In fact, this is a characteristic of all Greek philosophical-scientific thinking, science being subsumed to philosophy. For instance, the scientific concept of causality, through which the laws of science are formed, was conceived initially from a philosophical point of view which has created some failures to scientific explanations.
2. Aristotle's Theory of Science
Aristotle is the most important thinker of ancient Greek, the one who initiates the research in a series of new sciences, being the first who achieves a classification of sciences. He says that to know scientifically means to know the essence of the things, and to know the essence of things means to know their primary causes and principles. In the first paragraph of his Physics, Aristotle states this condition about natural sciences:1
In all disciplines in which there is systematic knowledge of things with principles, causes, or elements, it arises from a grasp of those: we think we have knowledge of a thing when we have found its primary causes and principles, and followed it back to its elements. Clearly, then, systematic knowledge of nature must start with an attempt to settle questions about principles.
Relating to the first princples, Aristotle states that there are four primary causes that help us to know the essence of a things. The four meanings of the cause are initially catalogued also in Physics:2
According to one way of speaking, that out of which as a constituent a thing comes to be is called a cause; for example, the bronze and the silver and their genera would be the causes respectively of a statue and a loving-cup. According to another, the form or model is a cause; this is the account of what the being would be, and its genera-thus the cause of an octave is the ratio of two to one, and more generally number-and the parts which come into the account. Again, there is the primary source of the change or the staying unchanged: for example, the man who has deliberated is a cause, the father is a cause of the child, and in general that which makes something of that which is made, and that which changes something of that which is changed. …