People, generally, do not choose their first language. We do not choose who our parents are, where we go to school, etc.
We don't even choose what we'll eat for the first few years of our lives.
Some people never get to choose where they live, who their spouse will be, or what books they will read.
Even those who DO choose which books they read only do so within a range - they can only read the books with translations available in the languages they read.
Many humans "think for themselves" - we make up ideas for ourselves (they may or may not be "new" in the sense that someone else has also thought similar things). But these too are limited to the kinds of things that humans think as humans - and these thoughts are likely to be different than what we would think or be able to think as dogs or angels.
Dogs probably don't think thoughts that we would verbalize with more than two small words. Angels can probably conceptualize aspects of reality that we can't imagine at all.
So there are constraints on what we think, what we can believe. We can only "believe" things we either learn by reading or have come up with ourselves. Both activities require time and effort which, for us, is limited.
Within those constraints though, there is a further question. Having come up with a given idea by creativity or learning, can we choose to accept or reject it.
Some beliefs are pretty obviously forced on us. For instance, if someone shoves a blue placard in front of our faces, we're hard-pressed to NOT believe that its there. We may say things like "it's imaginary" but the tendency to act as though it is there is very hard to avoid.
A second level of beliefs "simple abstractions from immediate knolwedge of things around us" like "I'm at my house" are similarly hard to characterize as "chosen".
A third level of beliefs "Abstract beliefs" where sensory data doesn't help us with decisions at all, seems to be made up mostly of predominant trends in the society in which we live - thus most Irish Nationals are Catholic, most Indians Hindu or Muslim, most Americans "protestant". For that very small segment of the population that bucks these trends (typically less than 20%) they choose their beliefs, for the most part, from competing sub-trends in their own societies (e.g. Libertarians in the USA or Tibetan Buddhists or Anarchists or Nihilists...). Finally a very, very small group of people in every society are unclassifiable within that society (that is, they have ideas that the predominant group of people in their societies don't recognize at all). These people tend to be outcasts in many ways, unable to function within society at large.
Do we choose which of these classifications we belong to? For the most part, no.
People seldom self-reflectively decide on which beliefs to have - they simply have them the same way that they believe that they'll need to eat sooner-or-later. It's just what they believe.
When people -do- self-reflectively decide on which beliefs to have, their choices tend to be so limited by time and familiarity that they choose something familiar and obvious.
So -within a very small scope - people can choose what beliefs they have, but have an overwhelming tendency NOT to do so.
Robbie Lindauer