Sentence:  The effect of a duelling spirit, on the heart that nourishes it, is of a most deplorable character. This self-vindicating spirit, gradually destroys a man's confidence in the integrity, intelligence, and enlightened impartiality of those around him. ... he will heed as little the lofty generous enterprises that kindle upon the moral world, as a caverned bear the luminous expanse of the glittering heaven. The spirit which he fosters has this tendency, and if the <WSD>fosterage</WSD> is persevered in, will have this effect. 
Meaning of the word marked with <WSD> tags:  The act of promoting or encouraging something.