The boundaries of the self are set by others. In other words, we base our knowledge of who we are upon observed similarities and disparities to the Other. You know that you are human because you are more akin to the other humans you observe than to dogs or to desks. You know that you are of a certain faith or lack thereof because you hear that in which other humans believe, and you agree or disagree. While logical elaboration arises in new ideas, the basics spring from outside observations of established systems coupled with personal observations that lead to said logical elaborations, etc. In other words, everything that you are, do, think, or believe ultimately comes from somewhere else. Even the loftiest of scientists (myself included) must work under the assumption that that which they perceive through their instruments is an accurate reflection of reality.
According to society, you know that you are of a certain race or gender because you are more akin to others of that race or gender than to humans who identify themselves as being of other races or genders (importantly, the definition of race or gender varies from society to society and is hence socially perpetuated without a necessary basis in science, which has ruled out gender and particularly race as absolutes or scientifically supported in most senses*).
In order to modify the self (such as our behaviour or our ideology), we look outwards. We appraise our behaviour based upon personal observation of the disparity between the desired effect and the resultant effect and strive to correct this. For example, we learn (and are taught by the Other) that one ought to be nice. Others then comment on our behaviour, guiding us to explore and eventually define the parameters of nice behaviour. In addition, we come to associate niceness with a certain type of response from others, such that we look for this response as feedback. Through the combination of external feedback and internal feedback, we understand niceness. From there, we decide to be nice, not to be nice, to idealise niceness, to degrade niceness, to weigh the value of niceness upon the environmental conditions, etc. Either way, internal analyses of our behaviour do not arise independently but ultimately stem from either an acceptance or a rejection—some sort of response—to a pre-existing idea.
In order to form our identities, we rely upon the external. Why is the pervasiveness of neuro-typicality, heteronormativity, colour-blindness, the “unbiased cishet white able male”, etc. such an issue? Why are microaggressions so lethal to self-identity? Why
*Race and gender: For clarification, there exist different “genders” and there exist certain genes that are more common in certain regions. Some of these, such as genes that may increase certain health problems at an observable rate and would be useful to treat health problems early in terms of allowing medical practitioners to more readily pinpoint potential issues, support an artificial delineation into “ethnic groups” with an inherent understanding that even genetic analysis does not form absolute distinctions and that race does not exist. Similarly, while vague “clouds” of gender identity exist (for example, trans individuals can become aware of their transness because they do not identify with the vague “cloud” of what a certain gender “brings with it”, disparate from gender roles) and medical practitioners would find it useful to distinguish generally between dfab, dmab, and intersex bodies on the basis of creating generalised disparate treatment plans that take into account approximate biological/hormonal/etc. differences, gender does not exist.