A while ago, my partner asked me what are my core values. What he meant by that was the values I had before I started studying philosophy, before I learned about politics, before religion, and so on. Well, that was a difficult question. How do you go back to your blank slate self and ask her what she thinks about the world and everything that it entails? Would she really be able to have values as adults understand them at this point? I was puzzled.
In philosophy, people learn about the importance of reaching a reflective equilibrium. This comes through careful analysis of theory and principles and reflection on your life, your experiences, your thoughts, etc. The final product, that is your judgment, should come from finding the equilibrium between what theory tells you is right and what you as a person can argue that is right without appealing to theoretic principles.
So, it's more or less obvious that by studying philosophy what one does is to depart from her initial "core values" and try to reach this reflective equilibrium. But even non-philosophers at least most of the time don't stick to beliefs they held when they were little. As you interact with the world, the world interacts with you.
I was a strange kid. My father started reading Plato to me when I was about 4. This added to my frustration: I couldn't go back to a pre-philosophical time since I was exposed to it so early. My core values seemed to be entangled with whatever I got to be exposed to at the time.
I still needed to come up with an answer, however. I only had pretty trivial points to make about how social construction primes us to have certain views and how the manifold of our values might consist out of values that aren't ours at all.
When I took my first philosophy class, the teacher and later my friend said that your thought is yours because you're having it, that you shouldn't worry about someone else having written down your thought before, even if that someone is a famous thinker.
I'm thinking it must be the same with values. A value is your core value because you're having it, it makes you who you are. The self-reflection that takes you back to when you were little to discover your initial, pure values might be a fun experiment, but doesn't yield helpful results. The process itself is flawed. What if you're confabulating? What if you're projecting? What if, what if.
My point is that our values are ultimately always under construction. Sure, we all have some meta-values that are more stable and help us build/modify our value system as a whole. But if you don't admit your values are subject to examination whenever that's needed, you're preventing yourself from changing.