2. The concept
1. What is a concept?
Logic studies concepts, judgments and reasoning.
A concept is the mental representation of an object. It is the simple capture of the essence of an object, but without affirming or denying anything. For instance, the ideas of a table, a pen, a computer and a blackboard are concepts.
There are two types of knowledge: the sensitive and the rational one.
The sensitive knowledge is acquired by means of senses (sight, hearing, etc.) and understands what is concrete and particular. For instance, I can see this pen, with this colour, size and special shape.
The rational knowledge is acquired by means of reason and understands what is abstract and essential. I have the general idea about what a pen is: an instrument to write.
Let us remember this sentence: There is nothing in mind that there has not been in senses before. Firstly we perceive things through senses and after we form an idea or rational knowledge.
The concept is the abstract idea (rational knowledge) based in sensitive knowledge.