By its formal character, philosophical knowledge pretends to arrive at the total comprehension of objects, that is, it does not investigate in things their immediate causes, productive of sensible phenomena (whose study belongs to the sciences), but tries to obtain knowledge of the Ultimate Causes, beyond which reason cannot ascend.
Science versus Philosophy
The Sciences study partial aspects of Being (taking this word in a broad sense, comprehending the Universe and the I), on the other hand, Philosophy studies Being in its totality.
We know things and beings, first in a simple manner by the senses, then in a more complex, reflexive manner, by their causes. We call the first vulgar knowledge and the second scientific knowledge.
We all begin with vulgar knowledge, but we perfect it more or less with our studies, our readings and the experiences that life provides us.
Philosophy considered as scientific knowledge (for being reflexive knowledge), tries to give us comprehension of things by their ultimate causes, employing for this reason.
Logic as Preparation
Before employing a complicated instrument, we must first know it and know how it functions, in order to use it correctly.
With reason, the philosophical instrument par excellence, we will do the same.
Its study, from the point of view of adequate employment for obtaining true knowledge constitutes FORMAL LOGIC, and working to solve the second we find MATERIAL LOGIC or THEORY OF KNOWLEDGE.
Logic, studying reason as an instrument of knowledge, enables us to introduce ourselves to philosophical study.
Speculative and Practical Philosophy
Taking into account that the end we propose is to acquire comprehension of things by their Supreme Principles, we can employ only the desire to know and we will make SPECULATIVE PHILOSOPHY, whose object will be being or the essence of things; but we can also employ reason trying to obtain from acquired knowledge, results useful for life, and we will then make PRACTICAL PHILOSOPHY, whose object will be the Absolute Good of Man.
The Branches of Philosophy
Now then, objects present themselves to our consideration, first as bodies, that is, taking units and differentiating among themselves by their forms and their physical-chemical properties.
The study of units and forms is proper to Mathematics, which referred to its ultimate causes, gives us the PHILOSOPHY OF MATHEMATICS.
The study of the physical-chemical properties of said bodies is the object in general of Natural Sciences, which referred to its supreme principles, gives us PHILOSOPHY OF NATURE.
But in that material world that constitutes Nature, we see emerging with truly differential character Man, who is the only being that knows and knows itself (affirmation we can make at least in these conditions of life).
The study of Man's internal world relative to his Psyche is the object of PSYCHOLOGY.