Plato, especially in the dialectic dialogues (f.i. Sofists), moving from the eleatic opposition of ‘Being’ and not ‘Being’ or, more exactly, of «what it is» to «what it is not », recognizes that, in this second term of the antithesys, the «not Being» is resolved in Being something else. "It is thus solved the mere negativity of each idea than the other, recognizes that, in this second term of the antithesis, the "not" will be resolved in '' be more. "It is thus explained the mere negativity of each idea than the other”.
Aristotle distinguishes alterity (understood generically as diversity, whereby all things are usually different) from the difference which is the dissimilarity between things of the same kind.
For the philosopher of idealism, ‘the something’, being characterized qualitatively, is in a negative logic contrast with'"other" than himself; he is not the other and then suffers the limit but, at the same time, this limitations kicks off a progressive alteration of its quality indefinitely (such as it happens in chemistry).
The term ‘alterity’ is often used in existentialism understood as alienation, division of the individual from himself.
On the contrary, for philosophers like Emmanuel Levinas (1905-1995) alterity not only is not a negative value, but it is the highest ethical one.
In particular, for Levinas, the first principle of ethics that, in this context, becomes metaphysical: If I do not violate my overarching categories, the mystery of the other, that is, if I do not bring it to a pre-determined and pre-judged essence, I get to a kind of knowledge that is real because it is a track of infinity.
Alterity is totally alien to the ego (split between self and the other) and, therefore, my experience will never be comparable to that of another person. I can not live the pain, joy and other limit experiences of another individual. For the Lithuanian philosopher ethics is the capacity of exit from the understanding as comprehension of the ‘other’ who is generally assimilated to himself and dispossessed of his alterity and diversity.
For many scholars, the reflection of Levinas on the ‘Other’ is one of the theoretical foundations of contemporary multiculturalism; that is it suggests a new and different vision of the relations between individuals and between cultures: as relations between diverse individuals, that - as such - should be recognized and valued. Only through this recognition it is possible to turn on an authentic communication between cultures, without hegemonic claims on each other. This is a fruitful perspective, through which, for example, it is possible to look in a new way the problems of relations between cultures that are caused by the migration processes taking place on a global scale.
The thought of Emmanuel Levinas developed, then, on two privileged sides: the 'phenomenological exercise of which he was among the first representatives in France and the Talmudic readings, inspired by Biblical and Hebrew themes. Starting from Heidegger, Levinas calls into question the primacy of the problem of Being, dominated by the principle of totality, to look in the appeal of alterity for the foundation of an authentic subjectivity.
Conducive to positively evaluate the alterity is the philosopher Salvatore Natoli (1942) who, reworking the Aristotelian concept of magnanimity, judges considering the good of the ‘other’ the best of all virtues: "The magnanimous person does not look down on others not because he underestimates them, but because he finds in the task he has set his measure "and" in this kind of self-control he becomes, paradoxically, more accessible to others; he becomes indirectly generous.
From Hegel on the problem of alterity and its relationship with the denial remained between the capital issues of dialectics. Different is the problem of alterity as a matter of the '' other person ', i.e. of the multiplicity of consciences.