The block of granite which was an obstacle in the path of the weak, becomes a steppingstone in the path of the strong.

Thomas Carlyle (1795–1881) Scottish essayist and historian

(Misattributed)

This quotation is widely attributed to Carlyle (e.g. (1896)), but, though sounding like something he might have said, it does not appear in his works.

Instead, it is actually a quotation from from G. H. Lewes, Life of Goethe, ch. 3 (1855) [emphasis mine]:

Instead, therefore, of saying that man is the creature of circumstance, it would be nearer the mark to say that man is the architect of circumstance. Our strength is measured by our plastic power. From the same materials one man builds palaces, another hovels, one warehouses, another villas; bricks and mortar are mortar and bricks until the architect can make them something else. Thus it is that in the same family, in the same circumstances, one man rears a stately edifice, whilst his brother, vacillating and incompetent, lives for ever among ruins; the block of granite which was an obstacle on the pathway of the weak, becomes a stepping-stone on the pathway of the strong.

George Henry Lewes (1817–1878) was an English philosopher and literary critic (and enamorata of Mary Ann Evans, a.k.a. George Eliot). Life of Goethe was one of his most popular works.

The cross-pollination to Carlyle is likely from Carlyle's deep friendship with Goethe and the numerous essays he wrote about the man and his works, as well as Carlyle being a pervasively-known writer of the period. A casual citation of the pith of this quote to a work called Life of Goethe could easily have become misattributed to the better-known Goethe enthusiast, Carlyle.