To begin with, it's important to note the difference in meaning between faith and belief. When I wake up in the morning, I believe that the floor will be solid under my feet, but I have no faith that it will be. It just possibly might not be.

Also, it is important to avoid an equivocation fallacy here. Faith that the bus will arrive because it is on a schedule and has consistently arrived in the past is not the same thing as faith in a supernatural force. The former is basically just a synonym for belief; the latter is something else entirely. There are individuals without faith in either, I believe, but it is important to be clear which definition is being suggested as a universal human behavior. Often the suggestion that one has the former type of 'faith', simple belief or conviction in recurring phenomena, is used to imply that one has faith of the latter type, which is where the equivocation fallacy comes in. Belief in demonstratable occurrences and belief in realms of existence beyond the natural are, clearly, very different things.

As a naturalist and something of a nihilist, I find it amusing when others suggest that I must have faith in something. I have belief in many things, but never to the point of surety--I don't even, really, have faith that the bus will arrive, just a conviction that it is very likely to do so. And I have no belief in anything at all which could be considered supernatural. And no, I similarly do not have faith in the nonexistence of the supernatural or the existence of a naturalist universe. Just belief.

The postulation that one cannot possibly exist without faith seems merely an act of projection: because one cannot comprehend existing without faith, one assumes others cannot exist without it either. Most such acts are rather obvious (if I were to project my disbelief in god onto society and assume that nobody can really believe in such a thing, that would be patently ridiculous), but when the vast majority of human society is a certain way, it's all too easy to assume the entirety of human society is that way, and those who claim otherwise are merely deluding themselves in some fashion.

We're not. I have no faith in anything at all. At least, as far as I can tell. Of course, I wouldn't say I have faith in this, my lack of faith.