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.