He conceived history as progressive, and inquired into the general causes which determine the gradual improvements of civilisation.

He dealt at length with the effects of climate and local circumstances, but unlike the French philosophers did not ignore heredity.

While he did not enter upon any discussion of future developments, he threw out incidentally the idea that the world may be united in a league of nations.
Posterity, he wrote, "may contemplate, from a concurrence of various causes and events, some of which are hastening into light, the greater part, or even the whole habitable globe, divided among nations free and independent in all the interior functions of government, forming one political and commercial system" (p.

287).
Dunbar's was an optimistic book, but his optimism was more cautious than Priestley's.

These are his final words: If human nature is liable to degenerate, it is capable of proportionable improvement from the collected wisdom of ages.