Complex sentence: Seurat's artistic personality was compounded of qualities which are usually supposed to be opposed and incompatible: on the one hand, his extreme and delicate sensibility; on the other, a passion for logical abstraction and an almost mathematical precision of mind.
Split into simpler sentences: Seurat's artistic personality was compounded of qualities which are usually supposed to be opposed and incompatible. On the one hand, his extreme and delicate sensibility, on the other a passion for logical abstraction and an almost mathematical precision of mind.