The reason is the capacity for cognition, thinking, moral judgment and aesthetic judgment. Disciplines that study these capacities are the theory of knowledge, logic, ethics, and aesthetics, respectively. Within these four general areas reason appears in many specific forms. These forms are "perfectly" known in philosophy, yet an unknown pattern has been noticed which shows us that they are all a variation of the same theme. It has been noticed that, in their essence, all of these forms are kinds of identity relations:

1. Truth is a relation of identity between the truth-bearer (e.g., a proposition) and truth-maker (e.g., a fact). (Russell and Moore in one period)

• "Correspondence holds between a proposition and a fact when the proposition and fact have the same structure, and the same constituents at each structural position" (Glanzberg), or essentially - correspondence is a relation of identity according to the structure;

2. Beauty

• Rhyme is a relation of identity between two or more words or phrases according to the final sounds;

• Rhythm is a relation of identity, according to the time interval between the beats;

• The golden ratio is a relation of identity between the ratio of the whole to the larger part and the ratio of the larger part to the smaller;

• Symmetry is an identity relation between two sides or halves;

• Anaphora is a relation of identity, according to the initial phrase or word in consecutive phrases, clauses, sentences, or verses. (e.g., "It rained on his lousy tombstone, and it rained on the grass on his stomach. It rained all over the place");

• Parallelism is a relation of identity according to the syntactic forms of two or more clauses sentences, or verse lines. (e.g., "The bigger they are, the harder they fall");

• Assonance is a relation of identity, according to the vowels between neighboring or words in close proximity to one another. (e.g., "sweet dreams", "hit or miss");

• Anadiplosis is a relation of identity between the last and the first word of two neighboring phrases or sentences. (e.g., "rely on his honor—honor such as his?");

• Epanalepsis is a relation of identity between a phrase or a word used at the beginning and the end of a sentence. (e.g., "Only the poor really know what it is to suffer; only the poor" or "The king is dead, long live the king");

• Meter (in literature) is (1) relation of identity between feet, according to their structure; and (2) relation of identity between verses according to the number of feet (and syllables at the same time) they have;

• Musical harmony is by definition "the combination of simultaneously sounded musical notes to produce a pleasing effect." Pythagoras noticed that instrument strings produce harmonious tones when the coefficients of their lengths are whole numbers. Modern research in physics confirms this revelation and shows that harmonic frequencies are all multiples of the same fundamental frequency. For example, notes at frequencies of 200, 300, and 400 Hertz are all multiples of 100. In physics, it is known that waves with different frequencies combine when traveling through the same medium and the resulting wave of this combination will have a regular structure which will be periodically repeated only if the frequencies are all multiples of the same fundamental frequency. The regularity and repetition of the resulting waves mean that its form and the moments when its amplitude reaches minimum and maximum values are regular and periodical. Each structure possessing regularity and repetition in itself contains identities, and harmony specifically can be understood as a super swift micro rhythm where the minimum and maximum values of the amplitudes play the role of beats. Perception of these identities is the cause of the beauty we experience in harmony. Otherwise, the resulting wave will be irregular and unpleasant to our ear.

• Etc.

This led us to an assumption that beauty in its essence is a relation of identity and the beauty of an object is the totality of identity relations it contains. This sub-thesis can be supported with the authority of Francis Hutcheson and the English poet Coleridge, who in his "On Poesy or Art" essay, writes: "…pleasure consists in the identity of two opposite elements, that is to say sameness and variety. …This unity in multeity I have elsewhere stated as the principle of beauty" (Coleridge).

3. Goodness

• Justice is a relation of identity between the value of the given and the value of the deserved;

• Distributive justice is essentially a relation of identity between the values of privileges, duties, and goods the individual receives on the one hand, and the value of the merits of the individual on the other hand;

• Retributive justice is essentially a relation of identity between the severity of the crime and the severity of punishment (‘An eye for an eye');

• Restorative justice is a relation of identity between the extent of damage and the extent of reparation;

• The golden rule is an identity between the treatment we want to receive and the treatment others receive from us;

• Happiness is a relation of identity between the actual and desired state;

• Love: there is no comprehensive and generally accepted definition of love, but I believe that the essence is best caught in the definition ascribed to Aristotle, according to which, "Love is composed of a single soul inhabiting two bodies." One soul in two bodies means that the bodies are identical according to the souls and according to this love, in its essence, can be defined as a relation of identity between two souls. The simplest confirmation for this view is the pleasant feeling of deep affection that takes over us when we meet a person with identical interests, views, tastes, desires, etc. This pleasant feeling can be liking, or if it is stronger – love. Simil simili gaudet. Hatred is a relation of difference in the same sense.

• Solidarity is a relation of identity in interests, objectives, and standards among members of a group or a class;

• Empathy is identification with the other according to the feelings or experiences;

• Each social group, category, or any other form of unity of reason in individuals, is formed on the foundation of some type of identity between individuals that constitute it; For example, ethnic groups are formed on the foundation of identity according to race, language, nationality, or culture, while the social classes are formed on the foundation of identity according to the social and economic status. Political parties are united by identical interests, identical ideology, etc.

This led us to an assumption that goodness in its essence is a relation of identity and that moral reasoning is in its core a process of identification and differentiation. From my humble knowledge of the history of philosophy, I cannot remember of another metaethical theory with a similar idea. However, the fundamental thesis of the so-called moral egalitarianism, which dominates the social, political, and moral philosophy since the end of the 20 century onward, is that equality is the essence of morality. On the other hand, every equality can be easily reduced to pure identity.

4. Thinking

• Induction is an identification between the known and unknown cases of the same class;

• The process of deductive thinking includes a series of identifications, first between the subject and the predicate from the first and second premises. Then the main identification, the essence of the deduction, between the two premises according to the middle term, wherein, with the application of Euclid's rule: ‘Things equal to the same thing are also equal to one another', as a conclusion we get identity between the major and the minor term. The deduction is a usage of the transitivity of identity

• An analogy is an identification between two relations of objects;

• One idea associates with another idea which is identical to it according to one or more properties;

• Each categorization and each classification occur according to a certain identity;

• Abstraction is the process of formulating generalized ideas or concepts by extracting common properties from specific examples. Common properties are in fact the content of the identity relation between specific examples. In order for the reason to extract these common properties, it needs to perform an identification.

• An analysis is based on identification because it clearly claims an identity, according to the meaning of analysandum and analysans;

• Etc.

This led us to an assumption that thinking in its essence is a process of identification and differentiation. I add differentiation because every identification is at the same time differentiation. As postulated in logic, the goal of the abstract logical thinking is reaching the truth. The goal and the result of the operation of identification can only be an identity, and according to this, truth, as seen previously, is nothing else but a relation of identity and when the reason recognizes truth it actually recognizes a relation of identity. This is a relatively new understanding which I offer considering the very well accepted fact that the first law of thinking is the principle of identity (A=A).

5. What I believe is a completely new idea in philosophy is that reason cognizes on the principle of identity and difference. An alternative theory of perception is offered which I will try to sketch it as short as possible:

It is based on the following scientifically confirmed process: light, sound, and other external world signals reach our sensory organs. Sensory organs turn light, sound, and the rest of the sensory signals into electric impulses. After they reach the brain, the processing of the electrical impulses by the reason begins and as a result, we obtain sensible things.

Now, what is a sensible thing? A proposed answer is that sensible things, as we know them, are segments of space and/or time with inherent uniformity or, what I allow myself to call them - "identities in themselves". I found support for this thesis in Plotinus' who in his ninth Ennead says that: "It is in virtue of unity that beings are beings" and that things "could not exist without an inherent unity."

Now I am reversing the process:

When the segments of space and/or time are uniform than the stream of electrical impulses, from which they are created, also must be uniform. And this stream is uniform when electromagnetic wave (light) or mechanical wave (sound) is uniform, from which is generated. The light is uniform when material reality in itself is uniform, from which it is reflected (with certain imperfections). One uniformity mirrors other uniformity. Reality as we know it and reality in itself, although completely different in nature, have identical identity-difference structure. Or, as Spinoza brilliantly put it: "The order and connection of ideas is the same as the order and connection of things".

Therefore, in order to create things which are uniformities in themselves which correspond completely to the uniformities in the series of electrical impulses, the reason must recognize where the series is uniform, where the difference begins, and divide it in sequences according to these boundaries. It actually identifies and differentiates, or in other words: the reason processes material provided by the senses on the principle of identity and difference. Sensible things are substantivized uniformities in the series of electric impulses.

Furthermore, widely accepted understanding in philosophy is that "…a universal will be anything which may be shared by many particulars…" (Russell). Since it is shared by them it is something they have in common, and a thing in common is, of course, what is identical between particulars. Universals are substantivized identities between particulars or, what I allow myself to call them - "identities between". It is fairly certain that in order to create these types of things it is necessary that the reason compares the particular or the less general things, to establish identities and differences between them, and to unite the identical ones in bigger wholes.

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These five sub-theses in their generality encompass almost the complete activity of the reason (epistemology, logic, aesthetic and ethic). Now the question arises, are these analyses sufficient to make a bold general conclusion that reason functions on the principle of identity and difference? Their perfect compatibility gives one another mutual confirmation.