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This topic examines the structure of a sound deductive argument, from its premise to its conclusion. The conclusion is only as compelling as the premises upon which it is based. Logic in itself does not solve the problem of verifying the basic assertions that are used to support arguments, for that, we need to use scientific enquiry. Since the philosophy of science and the scientific method are complicated topics, they are not covered in this discussion.

Propositions

A proposition is a statement that is either true or false. It pertains to the meaning of the statement, not to the arrangement of words used to convey that meaning. For example, "There a black belt in our class" is a proposition. "Our class has a black belt in it" is a rephrasing of the same proposition. Care must be used in rephrasing, since it is easy to change the meaning of a statement unintentionally by rephrasing it.

Arguments

An argument is "a connected series of statements used to establish a definite proposition." There are many types of arguments, however, for this discussion we are only concerned with the deductive argument. Deductive arguments are generally viewed as the most precise and the most persuasive. They provide conclusive proof of their conclusion, and are either valid or invalid. Deductive arguments have three stages: premises, inference, and conclusion.

Premises

A deductive argument requires a number of core assumptions, called premises, on which the argument is built. They are the reasons for accepting the argument. Premises are only premises in the context of a particular argument; in another argument, they might be conclusions.

You should always explicitly state the premises of the argument. Failing to do so is often viewed as suspicious, and will likely reduce acceptance of your argument.

The premises of an argument are often introduced with words such as "Assume", "Since", "Obviously," and "Because." You should get your opponent to agree with the premises of your argument before proceeding.

Using the word "obviously" in a premise is often viewed with suspicion, since it is sometimes used to persuade people to accept false statements rather than admit that they do not understand why something is obvious. Do not be afraid to question statements that people tell you should be obvious.

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