The argument from desire is an argument for the existence of God. It is most known in recent times through the writings of C. S. Lewis, for whom it played pivotal role in his own conversion to theism and thence to Christianity.

As a syllogism it can be expressed as follows.

The argument is not meant to be a proof. The conclusion may not necessarily be the only possibility satisfying the premises. Yet the argument from desire can be persuasive because the premises and conclusion can be not merely understood but "seen" in a much more direct way than similar arguments, such as the Ontological Argument. It is more directly applicable to the human experience.

The argument from desire has attracted criticisms from both religious and non-religious commentators; whilst using it as evidence for God's existence, Christian philosopher Thomas Aquinas did not consider it a valid argument for the existence of God on its own. In examining the use of the argument from desire in Aquinas's philosophy, historian Robert Pasnau criticises the argument as being "based on strong teleological assumptions few would accept today. It seems clear, contrary to his [Aquinas's] central assumption, that there are things in nature that have no point". Psychoanalyst Sigmund Freud likewise considered God to be no more than a psychological "illusion" created by the mind in an attempt to fulfil innate human desires, rather than an actual existing entity.

In logic and rhetoric, a fallacy is usually an improper argumentation in reasoning often resulting in a misconception or presumption. Literally, a fallacy is "an error in reasoning that renders an argument logically invalid". By accident or design, fallacies may exploit emotional triggers in the listener or participant (appeal to emotion), or take advantage of social relationships between people (e.g. argument from authority). Fallacious arguments are often structured using rhetorical patterns that obscure any logical argument.

Though an argument is not "logically valid", it is not necessarily the case that the conclusion is incorrect. It simply means that the conclusion cannot logically be arrived at using that argument.

Though often used unintentionally, fallacies can be used purposefully to win arguments regardless of the merits. Among such devices, discussed in more detail below, are: "ignoring the question" to divert argument to unrelated issues using a red herring, making the argument personal (argumentum ad hominem) and discrediting the opposition's character, "begging the question" (petitio principi), the use of the non-sequitur, false cause and effect (post hoc ergo propter hoc), bandwagoning (everyone says so), the "false dilemma" or "either-or fallacy" in which the situation is oversimplified, "card-stacking" or selective use of facts, and "false analogy". Another common device is the "false generalization", an abstraction of the argument that shifts discussion to platitudes where the facts of the matter are lost. There are many, many more tricks to divert attention from careful exploration of a subject.