Final answer:
Basil Hallward, upon noticing changes in the portrait that reflected the moral degradation of Dorian Gray, decided not to exhibit the portrait publicly, preserving the privacy of the sitter's corrupted soul.
Step-by-step explanation:
In the story involving Basil and Dorian's portrait, after noticing changes in the portrait that reflected Dorian's moral degradation, Basil Hallward became conflicted about his work. Initially proud of the painting, deeming it the pinnacle of his artistic career, the transformation it underwent caused him distress. Ultimately, Basil did not want to exhibit the portrait publicly, fearing its altered state mirrored something darker and could reveal too much about the sitter's (Dorian's) tarnished soul. He likely intended to keep it private, away from the judgement and scrutiny of the public and art critics. The novel 'The Picture of Dorian Gray' by Oscar Wilde delves deep into themes of aesthetics, morality, and the soul, which are personified through the changing painting.