All valid arguments have all true premises and true conclusions. If an argument is valid, then it must have at least one true premise.

The difference between syllogism and enthymeme is that enthymeme has one or two parts missing in a syllogism but with syllogisms they provide a logical way to lay out a claim and supports it. Enthymemes are not always deductive.

An example of inductive logic is, “The coin I pulled from the bag is a penny. Therefore, all the coins in the bag are pennies.” Even if all of the premises are true in a statement, inductive reasoning allows for the conclusion to be false.

If it’s being offered as a reason to believe another claim, then it’s functioning as a premise. If it’s expressing the main point of the argument, what the argument is trying to persuade you to accept, then it’s the conclusion. There are words and phrases that indicate premises too.

Valid: an argument is valid if and only if it is necessary that if all of the premises are true, then the conclusion is true; if all the premises are true, then the conclusion must be true; it is impossible that all the premises are true and the conclusion is false. Invalid: an argument that is not valid.

A deductive argument is said to be valid if and only if it takes a form that makes it impossible for the premises to be true and the conclusion nevertheless to be false. In effect, an argument is valid if the truth of the premises logically guarantees the truth of the conclusion. …

If an argument is valid, then (by definition) it’s impossible for its premises to be true and its conclusion false at the same time. Adding an extra premise cannot change that. That means there’s a possibility that the premises are true and the conclusion false.

If an argument is invalid then it will remain invalid if we add further premises in support of the conclusion. An argument is valid if and only if it is an instance of a valid argument form.

A good argument is one in which the premises are more plausible than the conclusion. This criteria means that an argument is not good if the conclusion is nothing more than a restatement of the premises, or when the conclusion rests upon a highly dubious (doubtful) premise or premises.

Circular reasoning (Latin: circulus in probando, “circle in proving”; also known as circular logic) is a logical fallacy in which the reasoner begins with what they are trying to end with. The components of a circular argument are often logically valid because if the premises are true, the conclusion must be true.

To summarize, a strong inductive argument is one where it is improbable for the conclusion to be false, given that the premises are true. A weak inductive argument is one where the conclusion probably would not follow from the premises, if they were true.