a posteriori
The term a posteriori ( Latin a 'from ... her' and Latin posterior 'the later, rear, younger, following' ; correctly Latin actually “a posteriore”) denotes an epistemic property of judgments in philosophy : judgments a posteriori are based on the Base of experience like. In contrast, there are judgments a priori . In general, all empirical judgments are considered a posteriori . The terms a priori and a posteriori have only had their meaning in judgment theory since the middle of the 17th century, but at the latest since Kant . Previously they were used in scholastic philosophy as a translation of the Aristotelian distinction between “proteron” and “hysteron” (condition and conditional).
Derived from the more recent usage, a posteriori knowledge denotes a knowledge that was gained through experience, in particular through sensory perception, in contrast to a priori or experience-independent knowledge (see a priorism ).
Premodern use up to Leibniz
For Aristotle , the contrast “proteron” and “hysteron” denotes the possible starting points for a proof. A proposition can be proven either on the basis of its consequences (hysteron) or on the basis of reasons (proteron). Aristotle also distinguished between an epistemic "proteron" that appears first in perception and an ontological-physical one that lies in the nature of the thing: the general is epistemically dependent on the individual things , but these are ontologically a consequence of matter .
Other pre-modern authors who dealt with a posteriori are Plato , Boethius , Averroes , Avicenna , Albertus Magnus and Thomas Aquinas ; It is implicitly also the case with Heraclitus in his examination of the 4 elements doctrine .
Leibniz distinguished rational truths, which are obtained from the understanding (a priori) solely through analysis, from factual truths, which are based on experience (a posteriori). Leibniz saw no real form of knowledge in empirical experience. He only assigned her the role of a stimulus or trigger for the activity of innate ideas. Even a "factual truth", i.e. H. In his opinion, knowledge about individual and concrete facts that has been gained from experience requires a more permanent basis than changeable nature. Facts, too, must be traced back to “truths of the understanding”, which thereby become the only a priori of all knowledge.
"Reasonable truths are necessary and their opposite is impossible, factual truths are contingent and their opposite is possible."
Judge a posteriori in Kant
Immanuel Kant crosses the epistemic properties of judgment with his semantic distinction between analytical and synthetic judgments. This creates four types of judgment:
| Synthetic judgments a priori | Synthetic judgments a posteriori |
| Analytical judgments a priori | Analytical judgments a posteriori |
Analytical sentences explain a term according to its characteristics. So is z. B. the sentence "The points on a circular line are equidistant from the center of the circle" analytically, because it follows directly from the Euclidean definition of the concept of the circle . This “explanatory judgment” does not need to be verified through experience. Accordingly, there are no a posteriori analytical judgments: the analytical relationship between the subject concept and the predicate concept is a logical “a priori” of the analytical proposition.
On the other hand, a statement like “This circle is large” can only be made if you look at a certain circle. Such a statement expands the knowledge about the subject of the sentence and is therefore synthetic a posteriori. Sentences of this kind are the subject of all empirical sciences. The sentence “A circular line is evenly curved”, on the other hand, is a synthetic a priori judgment: In the definition of the circle, the circular line is determined by the fact that all its points have the same distance from the center, but the uniform curvature is not one of its characteristics is determined by the definition, but it results from the definition and the properties of the geometric space.
The purpose of the distinction from Kant was to find the truth criterion synthetic judgments a priori, since with these new knowledge can be obtained independently of individual observations. To this Kant counted in particular the theorems of mathematics or generally valid theorems of the pure natural sciences, such as Newton 's laws in physics, as well as valid principles of the metaphysics of nature and ethics.
Current science and epistemology
Based on the ancient usage of the word, a posteriori theory formation is used when the facts to be explained by the theory have already occurred. A theory that was formed a posteriori initially only fulfills the criterion of explanatory power in terms of its scientific nature and has to prove itself in other respects (traceability, verifiability, falsifiability , predictive power).
An everyday example of the formation of a posteriori theory is the economic and stock market news: After an observed effect has occurred, possible causes for this development are discussed. Insights gained a posteriori are then converted into forecast models that can be checked against the historical data.
Knowledge a priori and a posteriori
In the context of modern epistemology , e.g. B. the scientific knowledge principle , the dualism of a priori and a posteriori knowledge is dissolved by the fact that observations must necessarily confirm the hypotheses (more precisely: must not falsify ), or that more general insights are hierarchically supported by more specific, more direct insights (evolutionary falsifiability ). Truth and knowledge therefore inevitably need both supports, and there is no more important , real , etc.
In the context of modern quantum physics (see e.g. the Copenhagen Interpretation ), the idea of the scientific knowledge principle with regard to truths is carried further: According to this, there are no defined truths per se in the form of determinable knowledge (neither a priori nor a posteriori ), but in principle only useful descriptions and probabilities . In quantum theories , hidden parameters, concepts and sub-theories necessarily appear: In the context of these theories (which are most powerful today with regard to the detailed behavior of matter), there is no way of describing the processes in the world well without these hidden concepts. And yet these hidden concepts are even interchangeable (sometimes even based on "senseless" infinities; see, for example: gauge invariance ), so they are not compulsory in their concrete form as "truth".
Web links
- Jason S. Baehr: A Priori and A Posteriori. In: Internet Encyclopedia of Philosophy .
- Keyword a posteriori in: Rudolf Eisler: Dictionary of Philosophical Terms (1904)
Individual evidence
- ↑ H. Scherpers, A priori / a posteriori, I. In: Historical dictionary of philosophy. Volume 1, pp. 462-467 ( Textarchiv - Internet Archive ).
- ↑ Gottfried Wilhelm Leibniz: Monadology. In: CJ Gerhardt (ed.): Philosophical writings. Volume 6, Weidmannsche Buchhandlung, Berlin 1890, reprint: Olms, Hildesheim 1978, 612.