Similarity (philosophy)

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Similarity is the agreement in one or more, but not all, properties.

The term refers to a relationship ( relation ) between two or more objects (in the broadest sense) that agree with regard to one or more, but not all properties ( features ) (cf. comparison (philosophy) ). The degree of similarity is measured according to the ratio of the common to the distinguishing properties. If no distinguishing characteristics can be found, one speaks of equality or identity .

  • Example 1: A car driver is similar to a bus driver in terms of driving a road vehicle. Both are similar to a train driver in terms of driving an earthbound vehicle. All three are similar to a flight captain and a skipper in terms of driving a vehicle. The similarity is greater when all drivers are transporting people; lower when partly people and partly only cargo are transported.
  • Example 2: In a strict sense, a person is only identical to himself at a certain point in space-time, in the course of time he is only similar because in the next second he thinks, sees something else, loses a hair, etc. .

The concept of similarity points to a deeper philosophical of problems recognizing the reality out. In addition, the concept of similarity touches different areas of both nature and human culture and perception .

Philosophical problem

In philosophical terms, similarity can be thematized in various ways:

Likeness and identity

Behind the term similarity hides an everyday problem of our knowledge , which has been known since Heraclitus , when he wrote: "We rise and we do not climb the same rivers" (Fragment 49a) Because each time it is different water that flows towards us . Because everything is in constant change, “things” are even at all times different from all other previous or future states of their own existence.

But if there are no completely identical things in the world, then every establishment of identity must in truth be based on the establishment of similarity , which the observer only mistakenly regards as identity, for example because he cannot discover any differences with his limited sense organs and measuring devices. From this perspective, identity is a matter for the beholder, whereas reality only knows something similar.

Similarity and Analogy

Similarity can be defined as a special case of an analogy .

The conclusion by analogy concludes from the correspondence or similarity of several objects in one respect to an agreement or similarity in another respect.

Similarity and Epistemology

Epistemologically, similarity is also addressed in several ways.

On the one hand, there is the question of whether something similar can only be recognized through something similar. This was represented by, among others, Pythagoras , Empedocles and Democritus . In his dialogue Kratylos , Plato describes the possibility that the recognized similarity of things described with symbols could presuppose the similarity of the symbols themselves.

The other is the more ontological question of the reason for the similarity of things. According to Plato, this is the similarity of the objects of perception with the ideas that the knowing person remembers in the anamnesis . According to scholastic philosophy , it is the analogia entis .

Furthermore, it is about the similarity of knowledge with what is known as the essence of knowledge as it sounds in the classic formula of truth as veritas est adaequatio rei et intellectus (cf. adequation theory ).

Among the philosophers of the modern age , it was David Hume who, in his study of the human mind, traced all arguments from experience back to experienced similarity. “We expect similar effects from causes that appear similar,” is the sum of all empirical conclusions , according to Hume .

The connection between similarity and identity has also been discussed in philosophy. Is similarity based on (partial) identity, identity on similarity or should the context be understood differently? And what follows from that?

The phenomenon “similarity” can be associated with the systems theory of Niklas Luhmann , because similarity is the basis of distinctions that are carefully considered in Luhmann's theory as the building blocks of knowledge. With the act of differentiation, Luhmann included the observer in his theoretical concept. Similarity is a phenomenon of distinction that cannot be fully explained without looking at the beholder.

Similarity as a natural property

An erroneous equation can also be useful for orientation. In a world in which no like exists, a living being can only orient itself if it has a sense of similarity with which it can react in similar ways to similar appearances. This feeling for similarity is the basis of all recognition and arises from the earliest stages of development of the sense organs. To distinguish conspecifics from enemies, to differentiate edible from inedible, males from females - these orientation tasks are vital for all living beings and can only be mastered by sensory organs that can quickly distinguish similar from dissimilar.

The erroneous equation of the like makes the fish snap at the fly-like bait , birds react quickly to fake enemies; by mistaken equation, twins are confused and fake banknotes are accepted as real money. The like is easily perceived as the same, but usually this fallacy is more useful than harmful, because most banknotes, enemies, and flies are real. The nature itself has innumerable forms of similarity produced - from the spiral shapes of the galaxies of the types of animals and plants and in the construction of the atoms inside.

Similarity in Human Culture


The principle of similarity also plays an important role in human culture . Only by establishing similarities can we grasp and classify objects in genres and categories . Every concept in human language encompasses an innumerable number of similar figures or facts - e.g. B. the word "tree" includes an infinite number of plants with similar properties.

But humans not only determine existing similarities in nature in order to orient themselves in it, but are also creators of similarities themselves. Its culture has consisted of similar products since the Stone Age, from the hand ax to industrial mass production . This also applies to his intellectual products such as language, music or art .

In language, for example, a word is always understood in the same way, even if it sounds at different speeds or pitches, even in different dialects , stammered by toddlers or drunkards - we grasp the similarity and understand it. It is the same with letters that are printed or scribbled, tiny or huge in infinite variations and always seen as the same figure, if only a certain similarity of structural features is preserved.

(Representative) painting is also based on the principle of similarity, for example in portraits or landscapes. The image is always similar to what is depicted in certain properties. Caricaturists show with just a few strokes how similarity made with the most economical means is still enough for us to be recognized (see also: Ikon ). Today photography often replaces the painter in depicting things in a similar way.

In music, the similarity already appears in the rhythm in the form of similar time values. All melodies can also be played and heard similarly at different pitches and speeds. The art of the fugue makes systematic use of this. Richard Wagner's leitmotifs and pop music carry the principle of musical similarity up to the present day, which in the field of pop music in particular is shaped and dominated by products that are essentially similar to one another, always knitted according to the same pattern and often manufactured in a “ cultural industrymanner .


“The similarity is once again likely to play the most important role in psychology . Perhaps up to now the similarity has been instinctively neglected because otherwise one would have had to see too early how far our logical or linguistic knowledge is below our scientific demands, how far our concept formation is from mathematical accuracy; because our language concepts are based on similarity, the mathematical formulas on equality. "

“All classification or language is based on similarity, not on equality, on similarity, not on equality, all our judgments or the application of language. But all logic , including the algebra of logic, is based on the mathematical concept of equality and is therefore a dangerous science. In order not to digress too far, it should only be mentioned briefly that the concept or the feeling of continuity also arises from the feeling of similarity alone. "

- Fritz Mauthner : Contributions to a Critique of Language, 1906

See also

Web links

Wiktionary: Similarity  - explanations of meanings, word origins, synonyms, translations

Footnotes and individual references

  1. a b Regenbogen / Meyer, Dictionary of Philosophical Terms (2005) / Similarity
  2. See Spree, in: Rehfus, Handwortbuch Philosophie (2003) / Conclusion by analogy
  3. Robert Spaemann : similarity , published in Journal of Philosophical Research , Volume 50, Issue 1/2 (January-June 1996), p 286 as an excerpt on the website of JSTOR
  4. ^ FH Bradley : On Professor James' doctrine of simple resemblance . Mind (NS) 2 (1893), 83-88
  5. William James : Mr. Bradley on immediate resemblance . Mind (NS) 2 (1893), 208-210