A priori and a posteriori Knowledge

  “A priori: (Latin = from the former) is deductive reasoning, ‘relating to or derived by reasoning from self-evident propositions; presupposed by experience.’ A priori usually describes lines of reasoning or arguments that proceed from the general to the particular, or from causes to effects. Whereas a posteriori knowledge is knowledge based solely on experience or personal observation, a priori knowledge is knowledge that comes from the power of reasoning based on self-evident truths.-Merriam-Webster Dictionary
  “A posteriori, Latin for ‘from the latter’, is a term from logic, which usually refers to reasoning that works backward from an effect to its causes. This kind of reasoning can sometimes lead to false conclusions. The fact that sunrise follows the crowing of a rooster, for example, doesn’t necessarily mean that the rooster’s crowing caused the sun to rise.”-Merriam-Webster Dictionary
  “Before Immanuel Kant, the Latin phrases a priori and a posteriori were used in Western philosophy to distinguish between arguments from causes and arguments from effects. Since Kant, a priori is defined as knowledge one has acquired independently of any particular experience, as opposed to a posteriori knowledge, which one derives from experience. Kant’s useage of the terms a priori and a posteriori highlights the antithesis between necessary truth (a truth that cannot be denied without contradiction), and contingent truth (a truth that depends on experience and therefore must acknowledge possible exceptions). In his Critique of Pure Reason (1781; 1787) Kant used these distinctions to explain the special case of mathematical knowledge, which he regarded as the fundamental example of a priori knowledge. An a priori judgment holds universally.
  “Interest in a priori knowledge is nearly as old as philosophy itself. Most people do not question how they can acquire knowledge—by observing, listening, or intuitive ‘feeling.’ But philosophers have long sought some special explanation. a prioriPlato maintained in his Meno and Phaedo dialogues that learning geometrical truths involved the soul’s recollection of knowledge possessed before its embodiment, when it could contemplate the eternal Forms directly. St. Augustine declared that such eternal ideas were in the mind of God, who from time to time gave intellectual illumination to human beings. René Descartes, going further in the same direction, held that all the ideas required for a priori knowledge were innate in each human mind. For Kant the puzzle was to explain the possibility of a priori judgments that were also synthetic (i.e., not merely explicative of concepts), and the solution that he proposed was the doctrine that space, time, and the categories (e.g., causality), about which such judgments could be made, were forms imposed by the mind on the stuff of experience.
  “In each of these theories the possibility of a priori knowledge is explained by a suggestion that there exists a privileged opportunity for studying the subject matter of such knowledge. The same conception recurs also in the very un-Platonic theory of a priori knowledge first enunciated by Thomas Hobbes in his De Corpore and adopted in the 20th century by the logical empiricists. According to this theory, statements of necessity are knowable a priori because they are merely by-products of rules governing the use of language.”–Encyclopedia Britannica

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