What is the contrast Thucydides is

What is the contrast Thucydides is drawing, between the explanation which was 'truest although least publicised', and the 'openly expressed grounds of complaint'? This question has been discussed over and over again, with an almost invariable failure to grasp the essential point. Virtually all recent writers have taken it for granted from the very start that the contrast is between an 'immediate cause' (or causes) and a more remote' or 'underlying cause', or (to put essentially the same idea a little differently) between a 'superficial cause' and a 'profound cause': the last is the way Momigliano puts it (OCWAH), and Kagan (OPW345) begins his chapter on "The Causes of the War' with the statement, ‘It was Thucydides who invented the distinction between the underlying, remote causes of war and the immediate causes’. There have been many similar formulations. In fact, Thucydides does not try to distinguish, either here or anywhere else in his work, between immediate or superficial and underlying or profound causes, and it is extraordinary that such an intention should so often have been foisted upon him,' sometimes with a good deal of grumbling about the supposed obscurity of his meaning, and even with accusations of paradox.