Here is an interesting quote: "Philosophy, like speaking prose, is something we have to do all our lives, well or badly, whether we notice it or not. What usually forces us to notice it is conflict." - Mary Midgeley.
Philosophy can be taken in two ways - as ideas or as method. I'm sure we all use both without, for the most part, giving it much thought. We do not know what we know. We all take a huge range of ideas for granted and only think about them consciously when they are challenged, either by a contrary opinion or by evidence. Of course, often we do not take the other opinion seriously or we avoid or reformulate the evidence so as to preserve our view. It is an important step in heightening intelligence to become interested in rather than resistant to contra-valuant material.
It has often seemed to me that more could be done within the education system to acclimatise young people to the art of thinking, so that they can at least enquire into their own and one another's opinions. The combined effects of a democratic ethos and social media, both of which tend to lead us to associate only with those who think as we do, tends to create a kind of intellectual blindness that must surely be dangerous in the long run. However, there is no doubt that we do pick up skills in thinking without ever knowing that we are doing so, alongside some bad habits.
Another example of not knowing what we know came out in a small item that has gone a bit viral on social media which is the observation that in English adjectives have to be in a certain order, namely,
so that one can have a quaint little old oblong blue Dutch wooden box, but if one rearranges the adjectives they either sound strange or change meaning. Thus
a Dutch blue wooden oblong box is possible but feels awkward and, in any case, one reads it as though 'Dutch blue' were a special colour and one mentally groups 'oblong box' as though it were a species of containers with some distinct meaning distant from ordinary boxes. In this way the ordering of adjectives gives us possibilities for shifting nuances of meaning without our having any conscious (until now) awareness that we were applying a grammatical rule.
A great deal of what we know is implicit.