What is called a sincere work is one that is endowed with enough strength to give reality to an illusion.

Jacob’s remark treats artistic “sincerity” not as autobiographical honesty but as aesthetic force. A work can be built from artifice—stylization, fiction, even deliberate illusion—yet still feel “true” if it has sufficient internal coherence, intensity, and persuasive power to make the imagined seem real to the reader or viewer. In this view, sincerity is an effect achieved by craft: the artist’s ability to confer reality on what is invented. The line also reflects a modernist sensitivity (common in Jacob’s milieu) to the paradox that art’s truths often arrive through fabrication rather than literal fact.