A few people called me on my diagram that suggests great faith occurs only with lots of thinking. Are there not countless simple-minded saints, whose lives manifested heroic faith without much evident intellectual effort?
I don't think a parallel objection regarding assent was raised. I suspect we all know what it's like to assent to something more or less strongly, and it seems reasonable to say that how "much" one believes something tracks with how strongly one assents to it.
Note, though, that for St. Thomas assent itself doesn't admit of degree. It is "an act of the intellect as determined to one object by the will;" by the time someone has moved from doubting through suspecting, past opining, and reached assenting, he "cleaves firmly to one side." (Hence he writes of "firm assent," firmam assensionem.)
So if you were silly enough to want to graph faith as a function of assent, faith would be zero where there was even fear of being wrong. And since strictly speaking assent doesn't vary -- it's either present or it's not -- faith can't vary directly with assent.
I propose, though, that there is something related to assent -- call it insistence -- that does vary, and that faith varies with. Insistence is the degree to which someone is prepared to insist that what he assents to is in fact true. I may assent to my neighbor's claim that his middle name is John -- that is to say, I may have no doubt that it's John -- but I probably wouldn't be too insistent; I wouldn't be ready to get into an argument with someone else over this. On the other hand, I may assent to my parents' claim of the date on which I was born, and with great insistence in the face of some counterclaim.
When insistence is a matter of belief -- that is, when it's related to a matter that I don't have personal, direct knowledge of (or in St. Thomas's phrase, when I lack "the certitude of sight") -- then I would say the more insistent I am the greater faith my belief reflects. I have more faith in my parents than in my neighbor.