Rev José Mario O Mandía
Is there anything beyond immediate inference? The answer is yes.
Immediate inference leads us to truths that are hidden in the truths we already know, but it does not get us very far. Our own experience shows that we do not only think through immediate inference, but through mediate inference.
Why is it called mediate inference? We will recall that in immediate inference, we are able to see the relation between two concepts without the need for a third concept to mediate. In mediate inference, however, we use a third concept to make the connection. This process of mediate inference is called reasoning (in logic, it is also called argumentation or logical discourse).
Reasoning is the third operation of the intellect as we have seen (the first is simple apprehension, the second is judgment.) The most basic form of reasoning consists of three ideas (expressed in language as “terms”) and three judgments (expressed in language as “propositions”).
From the two propositions “The fetus is a human person” and “A human person has the right to life” we come up with a third — the conclusion “The fetus has the right to life.” We are able to make the connection between the terms “fetus” and “right to life” through a mediator (called the “middle term”): “human person.” In fact, most of our life, we are making these connections; most of our life we need to “connect the dots.” That’s what we do when we reason out: we connect the dots.
When we are young, we know things in a scattered way. Other people, especially our parents, our teachers, and the good books we read help us to discover the links between concepts: they help us connect the dots. As we see more connections, we are able to think more clearly, decide more wisely, communicate more effectively. By connecting the dots of our scattered experience, we are able to see the big picture and we realize that behind the complexity, there is simplicity.
Reasoning always involves truths we already know which lead us to a truth that we previously did not know. The truths we already know are called the premises or antecedent, and the truth we previously did not know is called the conclusion or consequent.
What are the fundamental rules of reasoning? There are two general principles which can be expressed either from the point of view of the premises or from the point of view of the conclusion.
From the point of view of the premises:
Rule P1. Ex vero non sequitur nisi verum — truth necessarily follows from truth. If the premises are true the conclusions are necessarily true, provided that the reasoning process (we will study this later) is correct.
Rule P2. Ex absurdo sequitur quodlibet — anything follows from what is absurd or false. If the premises are false, the conclusion can either be true or false.
From the point of view of the conclusion:
Rule C1. A false conclusion necessarily means that there is some falsity in the premises or antecedent. The majority of errors happen because of false premises rather than faulty reasoning.
Rule C2. A true conclusion, however, does not necessarily mean that the premises are true. For example: a materialistic social policy (false premise) may promote families with more than two children because they see that this is economically beneficial to society. Christian social teaching, however, says that children are gifts, not mere tools to ensure economic progress.