The ominous double meaning here is that Charles will "make use of" Holroyd's total sublimation to a cause. In that sense Holroyd does indeed speak with "the voice of destiny" -- Charles' own destiny, and the destiny of all who fall prey to an overmastering dream-ideal.

On another level, the phrase "make use of what I see" is strictly materialistic, conveying something of the character of the material interests in their ceaseless transformation of the visible. This materialism goes against the grain of his wife, whose concern is precisely for the most invisible of things, the human soul.