Consider 2 blocks kept near each other on a table. Apply force on one, the other will move too. How does a child understand this, which it experiences?
Consider this – If you show a blue bag to a child and suppose it goes near it and explores it, and finds chocolates inside. It sees an identical blue bag later; it will think there are chocolates inside it too. Why? SAME FEATURE => SAME PROPERTY. Same colour and design bag, same contents!
In case of the blocks, when the child pushes one, the first one touches the second. Now touching is a sort of a loose conceptual analogy for “sameness” (oneness due to contact). So since the second block is now “same” as/with the first block, in some respect, and the first block moves (which it understands as due to direct application of force on it), the second block should also move. This is exactly like the bag and chocolates scenario. SAME => SAME.
So, is it so that the underlying concepts are the same whereas the actual form of reality in question might be different – say physical (as in the case above of blocks), abstract (colour and contents, as in the case above), numerical, geometrical, linguistic (words and sentences) etc.? Why not thus unify it all into naive sense (commonsense) rather than specialise things into cases like naive PHYSICS?