I must study politics and war that my sons may have liberty to study mathematics and philosophy. My sons ought to study mathematics and philosophy, geography, natural history, naval architecture, navigation, commerce and agriculture in order to give their children a right to study painting, poetry, music, architecture, statuary, tapestry, and porcelain. - John Adams

What does it mean??
I guess this is about different spheres of knowledge that are passed on from generation to generation so that the evolution occurs.
The father demands to read Politics and war—meaning , they are the prime issues of the prevailing scenarios of his times. And to bring peace for his next generation he must master them and solve the crisis. So that the children may have their “right” to read what they want. But in turn they should study something which may award the children’s children their “right” to study what the latter want! Which is arts, poetry , procaine etc. To study arts, the generation before must over come the obstacles of their times which can be resolved by studies in Navigation, Commerce, Naval Architecture, mathematics, sciences and history.

What a far-sightedness of the father.! For his grand children.
The literature is deemed to be the ultimate and most leisure time subject of studies. But u can have leisure only when, first, you have peace, and then , second, you have developed enough to overcome the hindrances of nature.! Study in natural sciences help to solve them . In the end you will have all the leisure to do what you want.
That’s a beautiful quote.