"I remember before we were married he used to potter about with a paint-box. But you never saw such daubs. We used to chaff him. He had absolutely no gift for anything like that."

"Of course it's only an excuse," said Mrs. MacAndrew.

Mrs. Strickland pondered deeply for some time. It was quite clear that she could not make head or tail of my announcement. She had put some order into the drawing-room by now, her housewifely instincts having got the better of her dismay; and it no longer bore that deserted look, like a furnished house long to let, which I had noticed on my first visit after the catastrophe. But now that I had seen Strickland in Paris it was difficult to imagine him in those surroundings. I thought it could hardly have failed to strike them that there was something incongruous in him.

"But if he wanted to be an artist, why didn't he say so?" asked Mrs. Strickland at last. "I should have thought I was the last person to be unsympathetic to -- to aspirations of that kind."

Mrs. MacAndrew tightened her lips. I imagine that she had never looked with approval on her sister's leaning towards persons who cultivated the arts. She spoke of "culchaw" derisively.

请教老师：在"I should have thought I was the last person to be unsympathetic to -- to aspirations of that kind." 

这里should have thought 是对过去的可能性推测吗？如果是，怎么理解含义呢？还有，为什么I imagine that she had never looked...中imagine谓语动词却使用了一般现在时呢？