First off, how do we inspire others to search for truth itself, instead of searching for self-gratification through ideas?
But in the same manner, what is it that inspires that sincere search for truth itself? Is it just a subtler form of self-gratification? If it's something deeper within us that inspires the search, does it have a name? Or other characteristics?
Simply put, what is it that motivates us? And what underlies the motives for our motives? And what then underlies those motives?
Why do we do the things we do?
I think that it depends upon each individual. I would further argue that each individual has different reasons at different times.
However - the very first impulse for the individual to aspire to some form of truth about what is around them is a selfish desire. It is sought for the satisfaction of the individual only. I doubt the initial impulse is altruistic.