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Inferences and Arguments

inference

When one tries to reason out, he makes inferences. Reasoning is a special mental activity called inferring. In other words, to infer is to draw conclusion/s out from the premises. The following are examples of inferences:

  1. You see smoke. Thus you infer that there is fire.
  2. You notice a vacant seat in your class. You infer that the one who seat there is absent.
  3. Originally, you were 50 in a group. On your counting there were only 47. You infer that there are 3 who are missing.

The reasoning process begins with inputs or premises and produces output or conclusion. Usually, inferences are based on different facts, data, information, ideas, figures, evidences, state of affairs, among others.

Logic considers all these things in a form of statements. This is to simplify the investigation of reasoning. The collection of these statements which treats inferences are called arguments.

Argument has a number of definitions if we refer to the English language. However, its definition that is relevant to logic is as follow.

An argument is a collection of statements, one of which is designated as the conclusion, and the remainder of which are designated as the premises.

In most cases, the premises of an argument are intended to justify or support the conclusion of the argument.

The statements or sentences that make up an argument are declarative statements or sentences.

The reason why declarative statements or sentences make an argument is because imperative, interrogative and exclamatory statements or sentences are not capable of identifying to be true or false.

The above given examples show on how these can represent an argument.

Consider the case of smoke-fire inference.

a. You see smoke (premise)

     therefore, there is fire (conclusion)

The argument herein consists of two statements, ‘you see smoke’ and ‘there is fire’.

The term ‘therefore’ is not strictly speaking form part of the argument. It only serves to designate the conclusion (‘there is fire’), drawn from its premise (‘you see smoke’).

This argument has only one premise.

Going to the missing-person inference, the corresponding argument is as follows.

c. Originally, you were 50 in a group (premise)

On your counting there were only 47 (premise)

    therefore, there are 3 who are missing (conclusion)

The foregoing argument consist of three (3) statements. ‘Originally, you were 50 in a group’, ‘on your counting there were only 47’, and ‘there are 3 who are missing’. Again, the term ‘therefore’ serves to designate conclusion drawn from its premises.

The collection of statements can be treated as an argument in principle if one tries to designate which particular statement serves as the conclusion. But not all collection of statements are intended to be an argument. There has to be a criteria in which we are going to distinguish arguments from other collections of statements.

Oftentimes, we can identify an argument since its conclusion is marked. One conclusion-marker is the word ‘therefore’. And there are other words aside from ‘therefore’ that are commonly used to mark conclusions of an arguments. These include ‘consequently’, ‘wherefore’, ‘hence’, ‘thus’, and ‘so’. These words usually indicates that what will follow is the conclusion of an argument.

There are also instances that an argument can be identified as such because its premises are mark with the word ‘for’, ‘since’ or ‘because’.

However there are times in which neither the conclusion nor the premises of an argument are marked. If this would be the case, it is hard to tell whether the collection of statements are intended to be an argument.

However, hereunder is a general rule of thumb that could be apply.

“In an argument, the premises are intended to support or justify the conclusion”.

In other words, when a person speaks or write advancing an argument, he/she expresses a statements (premises) believed to be true (conclusion), and he/she cites other statements serving as his/her reasons for believing on that statement (premises).

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The Task of Logic

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Logic maybe defined as the science of reasoning or correct thinking. It is a non-empirical science like mathematics. It is neither experimental nor observational science like biology, psychology or physics. Moreover, it does not employ the actual mental or physical process that occurred in thinking when one tries to reason out.

Despite that the aforestated empirical disciplines are more advance at present, nonetheless they could not thoroughly explain what goes on in the human being’s head when he reasons out. It cannot tell whether his reasoning is correct or incorrect.

To distinguish correct reasoning from incorrect reasoning wherefore is the task of logic.

In the introductory study of logic, often one will use categorical syllogism to distinguish validity and invalidity of an argument. It uses two concrete statements as premises and out of these produce a conclusion. This is how the reasoning process maybe thought of.

In drawing conclusions out of the premises 1, 2, 3, the details on the actual mental process is not therefore the proper concern of logic. Instead, to determine whether the conclusion on the basis of the premises is warranted correct is the logic’s concern.