But since the age of thirteen Deronda had associated the deepest experience of his affections with what was a pure supposition, namely, that Sir Hugo was his father: that was a hypothesis which had been the source of passionate struggle within him; by its light he had been accustomed to subdue feelings and to cherish them. 
But since the age of thirteen Deronda had associated his deepest affections with the assumption that Sir Hugo was his father. That theory had been the source of passionate struggle within him; by its light he had been accustomed to subdue feelings and to cherish them. 