http://www.newmanreader.org/works/grammar/chapter9.html

The Illative Sense: The ability to make conclusions based on inference, as opposed to hard facts and proof. That sense which allows faith to work.

Could you perhaps supply examples of conclusions based on hard facts and proof "sans" inference ? If you actually read Newman you would see that the Illative Sense is related to inference, not to "leaps of faith":

"...reason never bids us be certain except on an absolute proof; and such a proof can never be furnished to us by the logic of words, for as certitude is of the mind, so is the act of inference which leads to it. Every one who reasons, is his own centre; and no expedient for attaining a common measure of minds can reverse this truth;—but then the question follows, is there any criterion of the accuracy of an inference, such as may be our warrant that certitude is rightly elicited in favour of the proposition inferred, since our warrant cannot, as I have said, be scientific? I have already said that the sole and final judgment on the validity of an inference in concrete matter is committed to the personal action of the ratiocinative faculty, the perfection or virture of which I have called the Illative Sense, a use of the word "sense" parallel to our use of it in "good sense," "common sense," a "sense of beauty," &c.;—and I own I do not see any way to go farther than this in answer to the question. "

I'm afraid I just cannot make sense of the Cardinals writings, I'm working on it but there are too many words I don't understand at teh moment. -- ta

I'm not particularly qualified to summarise, but I'll try:

• We make inferences based on evidence.
• The act of inference is subjective.
• But we require absolute proof for certainty.
• Therefore we cannot hold anything with certainty.
• Certain types of inference, although subjective, seem reasonable based on disparate strands of evidence.
• This allows us to hold certain things with "certitude".
• The Illative Sense is the faculty by which we do this.

So, in a way it is the sense that allows science to work? Or indeed, lets you get by in the world without constantly questioning the 'truth' of everything -- ta

I take it to be the way we "know" things like, "My wife loves me," or, "The real world exists apart from my subjective experiences." Villainous Iagos or self-deceived philosophers might try to convince us that we can't really know these things with certainty, but the healthy response to them is, "Oh, bosh, just use your Illative Sense and you'll see it's true." -- Tom Kreitzberg

Wittgenstein, IIRC, invites us to distinguish clearly between the feeling of certainty and the claim of knowledge.

Do you feel certain that your dog loves you, or do you know that she does?

Not only am I not married, I'm also dog-less. Quite who there is that loves me, I've no idea.

But consdier: which pairs of answers make sense? Which don't?

• not sure, don't know
• not sure, do know
• sure, don't know
• sure, know.

Does the question make sense in the current context? How can you be certain which of the above, if any, make sense without the exercise of the faculty in question. -- ps (also wifeless, dogless, perhaps clueless too)

Well, about which proposition is it possible to be wrong? If someone asks you: do you know such-and-so, you can answer yes, or no, or maybe or any one of many things. And you could be wrong in each case. You might know, but not realise it, for example. And to justify your answer you need to wade into the quicksand of epistemology.

But suppose you answer yes. Then you are asked: are you sure? How can you be mistaken about this? You don't need to work out whether or not you're sure. You are or you aren't. And there's no justification to be had, or required.

I'm not sure I get your point (in fact I know I don't ;-)).

We're starting from the premise that you can't know anything with certainty. At the very least that would require unprovably true assertions such as "there is an objective reality that my senses can reliably interpret" (this is just an example ... you don't have to assert this particular thing, but you always make some unprovable assumptions). As you point out, you can still be sure of some things, since this requires no justification. However, I suggest most people like to think that they are being rational in their surety. They need a basis for certitude, and for most this has to do with consistency at some level. There is consistency in sensible experience. There is the scientific notion of experimental repeatability. There are reports of common experience from other people. None of these things can be ultimately reliable and, furthermore, a large amount of the evidence we weave into our conclusions is not from our direct experience, but is simply accepted on the authority of others. I suspect that a lot of the things we believe depend on which sources we consider to be authoritative.

At the end of the day, then, the things we are sure about rest on a foundation of direct experience, authoritative sources, and interpretation. When we weigh up the likely reliability of the various inputs, we are using our Illative Sense. Its what we use to determine if something is Convincing Evidence.

"You don't believe in me," observed the Ghost.

"I don't." said Scrooge.

"What evidence would you have of my reality beyond that of your senses?"

"I don't know," said Scrooge.

"Why do you doubt your senses?"

"Because," said Scrooge, "a little thing affects them. A slight disorder of the stomach makes them cheats. You may be an undigested bit of beef, a blot of mustard, a crumb of cheese, a fragment of an underdone potato. There's more of gravy than of grave about you, whatever you are!"