isn't it just obvious? We have to make decisions. Each decision is made (consciously or subconsciously) by weighing up the predicted outcome according to a set of values. Those values inevitably conflict, so they have in turn to be judged by a yet higher value. And so on until there is a top value.

You might think that some people change their values on a whim, but that in fact shows that something like their Self is their top value.

Unless our behaviour was completely random, I don't know how this could be any other way.

If you insist on a citation, I'll refer to St Augustine. Here's a popular culture level article about it https://www.huffpost.com/entry/augustine-sin-quote_n_56980d5...