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Like all disciplines, Philosophy has its own special terminology. To be a successful Philosophy student, you will need to learn this terminology and be able to use it appropriately in your writing.

To complete the tasks in this section, you will first need to study the following terms and their accompanying explanations.

A short glossary of terms:

  • proposition
  • premise
  • validity
  • evidence
  • conclusion
  • soundness
  • argument
  • objection
  • persuasiveness


A proposition is the content of an utterance or a belief. That is, a proposition is what is said when a sentence is uttered, or what is believed when a belief is entertained. A proposition is the kind of thing which can be assessed for truth and falsity. Some propositions are uncontroversially true or false, for example 'All Greeks are mortal' or 'All Greeks are immortal'. For other propositions, however, their truth or falsity may be harder to establish, e.g. 'All Greeks are lucky'.


A premise of an argument is one of the propositions from which the conclusion is jointly derived. In the following argument:

All Greeks are mortal

Socrates is Greek

Therefore Socrates is mortal

the premises are that "all Greeks are mortal" and that "Socrates is Greek".


Generally, an argument is valid if its conclusion follows from its premises. Thus, the validity of the argument is concerned with the structure of the argument, in particular about the connections which hold between the premises and the conclusion. Consider the following argument:

All Barbarians are immortal

Socrates is a Barbarian

Therefore Socrates is immortal.

Even though the premises themselves are false, they do guarantee the conclusion. So, this argument is valid.


Evidence is information that can be introduced to support the truth or falsity of a given proposition or claim. Evidence may be drawn from a variety of sources, e.g. sensory observation, testimony of others, chains of reasoning, and so forth. Invoking evidence in support of a proposition like 'All Greeks are mortal' would be straightforward enough; for a claim like 'All Greeks are lucky', it would be more difficult.


A conclusion for an argument is the proposition which is derived from the premises of the argument. More generally, a conclusion is the end product of an operation performed with propositions: reasoning, arguing, and the like. In the following argument:

All Greeks are mortal

Socrates is Greek

Therefore Socrates is mortal

the conclusion is that 'Socrates is mortal'.


An argument is sound only in the case that: 1) the argument is valid; and 2) all of the premises of the argument are true. (Sometimes, 2 may be weakened to the requirement that all of the premises of the argument are rationally acceptable, or the like.) So whilst the argument above ('All Barbarians are immortal; Socrates is a Barbarian; therefore Socrates is immortal.') may be valid, it is not sound.


In philosophy, an argument is typically a collection of propositions that lead, by some pattern of inference, to a conclusion. A simple example of an argument is the following:

All Greeks are mortal

Socrates is Greek

Therefore Socrates is mortal


An objection to an argument is a reason for rejecting the argument. In philosophy, an argument typically may be objected to on the grounds that it is:

  1. invalid,
  2. unsound, or
  3. unpersuasive.


Persuasiveness is the highest standard of acceptability for arguments. An argument is persuasive only in the case that: 1) it is sound; and 2) it does not suffer from some other kind of defect which would allow someone to reasonably reject its conclusion. In particular, a persuasive argument cannot be question-begging, i.e. it cannot assume what it is intended to establish. Clearly, the argument 'Socrates is Greek; therefore Socrates is Greek' cannot be persuasive, since it runs around in a very small circle.

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