one unavoidably substitutes for the observation statement a protocol statement which as such has a wholly different nature. 

VIII 
I believe that the problem of the basis of knowledge is now clarified. 
If science is taken to be a system of statements in which one's interest as a logician is confined to their logical connections, the question of its basis, which would then be a 'logical" question, can be answered quite arbitrarily. For one is free to define the basis as one wishes. In an abstract system of statements there is no priority and no posteriority. For instance, the most general statements of science, thus those that are normally selected as axioms, could be regarded as its ultimate foundation; but this name could just as well be reserved for the most particular statements, which would then more or less actually correspond to the protocols written down. Or any other choice would be possible. But all the statements of science are collectively and individually, hypotheses the moment one considers them from the point of view of their truth value, their validity. 

If attention is directed upon the relation of science to reality the system of its statements is seen to be that which it really is, namely, a means of finding one's way among the facts; of arriving at the joy of confirmation, the feeling of finality. The problem of the "basis" changes then automatically into that of the unshakeable point of contact between knowledge and reality. We have come to know these absolutely fixed points of contact, the confirmations, in their individuality: they are the only synthetic statements that are not hypotheses. They do not in any way lie at the base of science; but like a flame, cognition, as it were, licks out to them, reaching each but for a moment and then at once consuming it. And newly fed and strengthened, it flames onward to the next. These moments of fulfillment and combustion are what is essential. All the light of knowledge comes from them. And it is for the source of this light the philosopher is really inquiring when he seeks the ultimate basis of all knowledge. 
If you do know that here is one hand, we'll grant you all the rest.
When one says that such and such a proposition can't be proved, of course that does not mean that it can't be derived from other propositions; any proposition can be derived from other ones. But they may be no more certain than it is itself. (On this a curious remark by H.Newman.)
From its seeming to me - or to everyone