Logic is defined as the science of correct reasoning. As a science, it provides methods and principles for distinguishing good (correct) from bad (incorrect) reasoning.[i] But why do we exactly need to know these methods and principles? It is for the simple reason that we care to be correct. The human mind always strives for the “truth.” It is precisely this “truth” that correct reasoning aims for. But what exactly is “truth”?
We say that something or a statement is true if it coincides with reality. If I saw a poodle, for example, and it is for a fact that it eats meat, then a true statement basing from what I perceive would be “The poodle is a carnivore.” Truth then is defined as the correspondence of the mind to reality. Thus, if what is thought in the mind does not coincide with the reality, then it is said to be false.
The simplest act of the mind to attain truth is judgment. When I affirm (or deny) an attribute to a subject, I am making a judgment. When I “think” for example that “The poodle is a carnivore” I am affirming the attribute “carnivore” to the subject “poodle.” My act of affirming this description to the house is a judgment. Now this judgment can be true or false. In this case (given the condition is indeed followed) it is true.
Even before the mind makes a judgment it has already done a simple comprehension. Taking the same example above, even before I made the judgment “The poodle is a carnivore” I already conceived individually the notions of “carnivore” and “poodle.” Thus my simple apprehension of the notions “carnivore” and “poodle” is a more elementary act of my mind than my judgment. It is only when I affirm the attribute carnivore to the subject poodle that I will actually make a judgment.
Now if I make a series of judgments following an orderly structure and flow, then I make an inference. For example,
All dogs are carnivores
All poodles are dogs
Therefore, all poodles are carnivores.
In other words, inference is the process of deducing or extracting a judgment from previous judgments.
Looking now at the whole process of reasoning, we first have simple apprehension, then judgment and lastly inference. Nevertheless, these are only “acts” of the mind. Unless they are verbally expressed, they cannot be evaluated through the logical methods and principles. The end products or verbal expressions of the three acts are term/name (for the notion conceived in simple apprehension), proposition (for judgment), and argument (for inference). In Traditional Logic, syllogism is the typical format of the arguments (as seen in the example above). It is composed of three propositions.
One of the fundamental principles of traditional logic is that “a proposition is always composed of two terms, the subject and the predicate.” In the proposition “All poodles are carnivores”, carnivore is the predicate because it is that which is predicated (affirmed/denied) to the subject poodle. The poodle is said to be the subject because it is the object being affirmed (or denied) of the attribute “carnivore.”
Arguments always have two parts, the conclusion and the premises. Otherwise, it is not an argument. The conclusion is the statement supported by previous statements. Premises, on the other, are the statements that support the conclusion. Referring to the example above, the conclusion is “All poodles are carnivores” and the premises are “All dogs are carnivores” and “All poodles are dogs.”
