What did love have to do with Ruth's divergent views on art, right conduct, the French Revolution, or equal suffrage?
They were mental processes, but love was beyond reason; it was superrational.

He could not belittle love.

He worshipped it.
Love lay on the mountain-tops beyond the valley-land of reason.

It was a sublimates condition of existence, the topmost peak of living, and it came rarely.

Thanks to the school of scientific philosophers he favored, he knew the biological significance of love; but by a refined process of the same scientific reasoning he reached the conclusion that the human organism achieved its highest purpose in love, that love must not be questioned, but must be accepted as the highest guerdon of life.