Compare with Decoud, who declared love "the supreme illusion."

On the surface, we read this complex line to mean that Monygham's love for Mrs Gould warms his heart, even though he has no "illusions" of achieving her, because of the "misfortune" of her marriage that forever silences his lips.

On the deeper level, however, "love" refers to his love for the subjective human soul, and this line completes his bond with Mrs Gould. The "enlightening" (i.e., disillusioning) yet "priceless misfortune" of this love, is that the beautiful subjective soul can only flower in the oppressive world. The alternative to the oppressive world, as both Monygham and Mrs Gould know, is a predatory anarchy.