If personal taste is something that emerges somewhat chaotically from personal experience and potentially genetics, then how can it belong to oneself and truly be personal? Surely, we don't like to think of our tastes as random; on the contrary, they define us. And yet if our tastes are something rational, then we might indeed be able to dispute them with some level of objectivity - some tastes would just be bad or good, and this could be proven. Clearly this isn't the case - so it seems personal taste is neither a chaotic result of our interaction with our life experience, nor some sort of rational conclusion on the subjects of the taste. What, then, is personal taste?

I think this is a fine question or questions.

Consider first the issue of whether what you are calling taste can be subject to proof or at least rational dispute. It may be that what you mean by "taste" simply means a desire or aversion to (for example) limes or apples, something which lacks standards to settle (assuming neither is a poison, etc). But if "taste" includes any kind of desire (the desire for justice versus the desire for mercy and so on), then many philosophers would claim (on all sorts of grounds) that we can rationally debate such matters. You might check out the work of John Rawls on one promising model of how one might adjudicate competing tastes.

On the second issue about when a taste or desire is one's own.... Perhaps the answer lies in terms of volunatary choice or consent or identification with the tastes or desires that you have. Consider the following possibility: each of us develops different tastes or desires, whether these are through nature or nurture, design or chaos, brain washing or accident, rational dispute or irrational impulse. But when a taste or desire becomes one's own or (as you put it) personal, this seems to be a case of when a person has (in some way) voluntarily chosen or consented to or identified with the taste or desire as one's own. So, imagine I have a desire to worship God. But imagine this is something I have never questioned or consented to; I was simply brought up that way. We might in that case think that my desire is not so much personal or voluntary as much as it is the desire of my community. And the same would be true if I had a desire to deny the existence of God; my atheism would not be reflection of MY particular, voluntary thought, but something I inherited or picked up from my community. I suggest that making a desire one's own involves consenting to it or identifying with it as when someone as an adult identifies themselves as (for example) a theist or atheist or whatever.... On this point, you might check out the work of Harry Frankfurt (Princeton University).

So, when you ask "What, then, is personal taste?" I suggest that some tastes or desires can be rationally debated and chosen and which tastes are authentic and personal to you depends on which tastes or desires you identify with or choose. If someone has a taste or desire that they do not choose and they find opposed to their deepest values, then those tastes or desires are still theirs, but those in such a state are (I suggest) in a fragmented, divided condition that will be difficult to sustain.

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