Contingency (philosophy) in the context of "Modal logic"

Existence is the state of having being or reality in contrast to nonexistence and nonbeing. Existence is often contrasted with essence: the essence of an entity is its essential features or qualities, which can be understood even if one does not know whether the entity exists.

Ontology is the philosophical discipline studying the nature and types of existence. Singular existence is the existence of individual entities while general existence refers to the existence of concepts or universals. Entities present in space and time have concrete existence in contrast to abstract entities, like numbers and sets. Other distinctions are between possible, contingent, and necessary existence and between physical and mental existence. The common view is that an entity either exists or not with nothing in between, but some philosophers say that there are degrees of existence, meaning that some entities exist to a higher degree than others.

In philosophy (often specifically metaphysics), the absolute, in most common usage, is an absolute perfect, self-sufficient reality that depends upon nothing external to itself. In theology, the term is also used to designate the supreme being or God. While the notion of the absolute varies across traditions and thinkers, it generally signifies something that transcends all forms of limitation, relativity, and contingency.

Social theories are analytical frameworks, or paradigms, that are used to study and interpret social phenomena. A tool used by social scientists, social theories relate to historical debates over the validity and reliability of different methodologies (e.g. positivism and antipositivism), the primacy of either structure or agency, as well as the relationship between contingency and necessity. Social theory in an informal nature, or authorship based outside of academic social and political science, may be referred to as "social criticism" or "social commentary", or "cultural criticism" and may be associated both with formal cultural and literary scholarship, as well as other non-academic or journalistic forms of writing.

A conditional sentence is a sentence in a natural language that expresses that one thing is contingent on another, e.g., "If it rains, the picnic will be cancelled." They are so called because the impact of the sentence’s main clause is conditional on a subordinate clause. A full conditional thus contains two clauses: the subordinate clause, called the antecedent (or protasis or if-clause), which expresses the condition, and the main clause, called the consequent (or apodosis or then-clause) expressing the result.

To form conditional sentences, languages use a variety of grammatical forms and constructions. The forms of verbs used in the antecedent and consequent are often subject to particular rules as regards their tense, aspect, and mood. Many languages have a specialized type of verb form called the conditional mood – broadly equivalent in meaning to the English "would (do something)" – for use in some types of conditional sentences.

The Proof of the Truthful (Arabic: برهان الصديقين, romanized: burhān al-ṣiddīqīn, also translated Demonstration of the Truthful or Proof of the Veracious, among others) is a formal argument for proving the existence of God introduced by the Islamic philosopher Avicenna (also known as Ibn Sina, 980–1037). Avicenna argued that there must be a "necessary existent" (Arabic: واجب الوجود, romanized: wājib al-wujūd), an entity that cannot not exist. The argument says that the entire set of contingent things must have a cause that is not contingent because otherwise it would be included in the set. Furthermore, through a series of arguments, he derived that the necessary existent must have attributes that he identified with God in Islam, including unity, simplicity, immateriality, intellect, power, generosity, and goodness.

Historian of philosophy Peter Adamson called the argument one of the most influential medieval arguments for God's existence, and Avicenna's biggest contribution to the history of philosophy. It was enthusiastically received and repeated (sometimes with modification) by later philosophers, including generations of Muslim philosophers, Western Christian philosophers such as Thomas Aquinas and Duns Scotus, and Jewish philosophers such as Maimonides.

Future contingent propositions (or simply, future contingents) are statements about states of affairs in the future that are contingent: neither necessarily true nor necessarily false.

The problem of future contingents seems to have been first discussed by Aristotle in chapter 9 of his On Interpretation (De Interpretatione), using the famous sea-battle example. Roughly a generation later, Diodorus Cronus from the Megarian school of philosophy stated a version of the problem in his notorious master argument. The problem was later discussed by Leibniz.