Do you really believe that there is any truth that you are going to get 7,511,772,360 (the number on the rolling world census at the time of writing) people to agree to? That includes new born infants, who are people. So perhaps we should cut off your question at some later age, say 18. But how will this age be decided? I think probably people have their own views because they have their own ideas, and they have their own ideas because their experiences are different and they are very different people anyway. Still, most people, though by no means all, accept elementary mathematics and the elementary ethics of everyday life. There are standards of evidence and argument that apply to both, to ethics in practical settings and to mathematics in theoretical ones as well. It seems very improbable that short of the coming of the Kingdom of God everyone will agree on everything. But that doesn't mean that what they should agree on, because it is true, isn't true.

Your argument is: (1) Our senses and perception are subjective. (2) Everything we know is based on on our senses and perceptions. Therefore (3) Everything we know is subjective. There is a well-known difficulty with this argument. It equivocates on "subjective". In the first premise "subjective" means something like the innocuous "possessed by a subject", but in the conclusion it is presumably taken to mean the toxic "not having any objective truth". There is also a doubt about the second premise. Many philosophers accept the idea of "a priori" truths, that is, truths that hold independently of experience, including mathematical truth and perhaps ethical truths, if there are any.

Descartes sought certainty because he thought that if we know something with certainty, then it must be true. And he was right, if only because 'S knows that p ' implies p , so that in 'We know with certainty that . . .' the phrase "with certainty" is redundant; there is no such thing as uncertain knowledge. I suspect that the sense of your question may be Cartesian: is it the case that certainty implies truth? There are several concepts to sort out here: 'We know for sure, or for certain, or with certainty that . . .', 'I am certain (sure) that . . .', 'I feel certain, sure, that . . .', 'It is certain that . . .' (but not 'It is sure that . . .') There is a very useful paper by G.E. Moore called "Certainty" that might be helpful here, which is sensitive to distinctions of this kind. Sean is right in his response above that psychological certainty or "feeling certain" may not be a mark of truth, though I wonder whether anyone has troubled to test the correlation empirically in...

You write that facts and ideas are very different things. (You also contrast beliefs and facts to make the same point, so perhaps you believe that beliefs are ideas.) From this you infer a difficulty about the possibility of ideas and facts corresponding to one another. 'Facts and ideas are very different things', you write, so 'how can they "correspond" to each other?' Consider, though. Written notes on a stave are very different from the sounds that we hear, but why should that stop them "corresponding" to sounds? Aunts and nephews are very different kinds of beings, but that need not stop them corresponding. You put "correspond" in scare quotes, and here you seem to me to be on the right track. We need to know what correspondence is. What is say a 1:1 correspondence?