How do we identify arguments in real life? There are no easy mechanical rules, and we usually have to rely on the context in order to determine which are the premises and the conclusions. But sometimes the job can be made easier by the presence of certain premise or conclusion indicators. For example, if a person makes a statement, and then adds "this is because ...", then it is quite likely that the first statement is presented as a conclusion, supported by the statements that come afterwards. Other words in English that might be used to indicate the premises to follow include :
The concept of validity provides a more precise explication of what it is for a conclusion to follow from the premises. Since this is one of the most important concepts in this course, you should make sure you fully understand the definition. In giving our definition we are making a distinction between truth and validity. In ordinary usage "valid" is often used interchangeably with "true" (similarly with "false" and "not valid"). But here validity is restricted to only arguments and not statements, and truth is a property of statements but not arguments. So never say things like "this statement is valid" or "that argument is true"!