As all probably know, Jack Silver passed away about one month ago. The announcement released, with delay, by European Set Theory Society includes a quote by Solovay about his belief on inconsistency of measurable cardinals and $ZFC$:
As Prof. Robert Solovay recently put it: "For at least the last 20 years, Jack was convinced that measurable cardinals (and indeed $ZFC$) was inconsistent. He strove mightily to prove this. If he had succeeded it would have been the theorem of the century (at least) in set theory."
I was curious to find out what convinced him to not believe consistency of $ZFC$ and what I kind of attempts he tried, of course I found nothing.
Is there any published or unpublished note about his belief and approach, or possibly his philosophy toward it?