Introduction to Logic:

Introduction to Logic:

The term “logic” is used quite a lot, but not always in its technical sense. Logic, strictly speaking, is the science or study of how to evaluate arguments and reasoning. Logic is what allows us to distinguish correct reasoning from poor reasoning. Logic is important because it helps us reason correctly — without correct reasoning, we don’t have a viable means for knowing the truth or arriving at sound beliefs.

Logic is not a matter of opinion: when it comes to evaluating arguments, there are specific principles and criteria which should be used. If we use those principles and criteria, then we are using logic; if we aren’t using those principles and criteria, then we are not justified in claiming to use logic or being logical. This is important because sometimes people don’t realise that what sounds reasonable isn’t necessarily logical in the strict sense of the word.

Why bother to learn more about logic and arguments?

The most immediate and obvious benefit from such a study is that it can allow you to improve the quality of the arguments you use.

A second and closely related benefit will be an improved ability to evaluate the arguments of others. When you understand how arguments are supposed to be constructed and also how they shouldn’t be constructed, you will find all sorts of bad arguments out there.

Although you may not realize it immediately, there are arguments all around us vying for our attention and acceptance. We hear arguments that we should buy car A rather than car B. We hear arguments that we should vote for politician Smith rather than for politician Jones. We hear arguments that we should adopt this social policy rather than that social policy.

In all of these cases, people are making (or should be making arguments — and because they are trying to get you to believe their conclusions, you have to be able to evaluate those arguments. When you can identify bad arguments, it will be easier for you to free yourself from beliefs which are not well founded. It also allows you to challenge people making claims which you think are suspect, but you would otherwise have difficulty in explaining why.

Arguments:

An argument is a deliberate attempt to move beyond just making an assertion. When offering an argument, you are offering a series of related statements which represent an attempt to support that assertion — to give others good reasons to believe that what you are asserting is true rather than false.

Here are examples of assertions:

1. Shakespeare wrote the play Hamlet.

2. Euthanasia is wrong.

3. God exists.

4. Prostitution is immoral.

Sometimes you hear such statements referred to as propositions.

An argument consists of a conclusion (which is what is being argued for) and a premise or premises which are the considerations which are being offered in favour of the conclusion.

For example:

Socrates is a man. All men are mortal. So, Socrates is mortal.

The premises of this argument are that “Socrates is a man” and that “All men are mortal“. The conclusion is that “Socrates is mortal“.

Note: the conclusion of an argument need not come at the end. It might come at the beginning, as in:

Socrates is mortal, for all men are mortal, and he is a man.

Or in the middle, as in:

Socrates is a man, and as such he is mortal, for all men are mortal.

An argument can be broken down into three major components: premises, inferences and a conclusion.

Premises are statements which are supposed to set forth the reasons and/or evidence for believing a claim. The claim, in turn, is the conclusion: what you finish with at the end of an argument. When an argument is simple, you may just have a couple of premises and a conclusion:

1. Doctors earn a lot of money. (premise)

2. I want to earn a lot of money. (premise)

3. I should become a doctor. (conclusion)

Inferences are the reasoning parts of an argument. Conclusions are a type of inference, but always the final inference. Usually an argument will be complicated enough to require inferences linking the premises with the final conclusion:

1. Doctors earn a lot of money. (premise)

2. With a lot of money, a person can travel a lot. (premise)

3. Doctors can travel a lot. (inference, from 1 and 2)

4. I want to travel a lot. (premise)

5. I should become a doctor. (conclusion. Inference from 3 and 4)

Once we understand what makes up an argument, and what does not, we can learn to critique arguments to determine if they are sound or valid.