Etched in Jell-O.

"Are politics a science or an art?"

Art with scientific overtones. “Art” seems to be a human science with so many unknown quantities that artistic creativity is known only to the few through intuition. Artistic appreciation is more widespread than creativity. Science will get better at it.

"Do we better know the present than the past?"

Clearly we “know” the present only as well as we “know” the past.
We have perspective on the present only through understanding the past.
To understand either is to understand both.
(To understand either is to understand Man.)

"Defending one's rights is it the same as defending one's interests?"

All rights are interests, not all interests are rights. Therefore defending one’s rights are defending interests, in the sense that giving up rights is diminishing oneself. Unless one gains a bigger right or interest.

(If guns could be eliminated from society, it might be that giving up the right to have a gun, should it exist, could enhance another right, the right to life, liberty and the pursuit of happiness. In that case, defending the “right” to own guns might diminish another “right”, to life, liberty and the pursuit of happiness.)

"Is language diversity an obstacle to understanding the people?"

Mixed. If all parties are fluent, it is an aid. There is a lot of information about a culture in it's language. If any party is not fluent, it is an obstacle.