Science makes many presuppositions, even suppositions that are accepted and posited as suppositions by scientists themselves. They acknowledge these assumptions as assumptions in order to make certain calculations about the universe. But there are more fundamental presuppostions that are not seen by science. The most fundammental presuppostion is the belief that the world is composed of physical objects. Science believes that the objective is the primary state of affairs -- what Kant called "the thing in itself" -- and that a subject (that is, subjectivity) is somehow added to this preexisting objective state of affairs. In truth however, just as a subject cannot exist without a world, neither can a world exist without a subject. What is taken as preexisting objects in truth only gain their existence, and thereby enter time, retroactively, through the experience of a being for whom time and existence are realities. The subject is essentially a clearing through which phenomena are freed from the oblivion in which they formerly "were," and only by being freed in this way do they show up as what they are. What science posits as preexisting "objects" of nature is actually a theoretical modification in the attitude of the subject, in which the primordial phenomenon is stripped of its phenomenological content. This is accomplished by a process of theorizing. I begin with the whole (science instead begins with parts, particles, atoms, molecules, elements, cells, etc.) -- that is, with environmentality. I then single something out -- the hammer. Beginning with this hammer that I have singled out as an object of investigation, I begin to theorize: the hammer is brown, brown is a color; color is a genuine sense datum, a sense datum is a result of physical or physiological "processes," the primary cause is physical, this cause objectively is a determinate number of electromagnetic waves/photons that travel to my eyes through the air, the air is made up of simple elements, linking these are simple laws, the elements are ultimate, the elements are something in general (the ultimate element, previously and erroneously believed to be the atom, is now believed to be these irreducible vibrating strings as explained by string theory, but who knows what science will posit as the "ultimate element" fifty years from now). There is an assumption in science that if we thoroughly objectify nature we could learn what these things are. But objectifying a given phenomenon is precisely how you don't find out what it is. The hammer is objectified -- and hence tacitly modified -- by treating it as an object of investigation. But as soon as I adopt this scientific attitude and turn the hammer into an object of investigation, I have thereby placed it in a different context. I have now placed it in a theoretical-scientific context. I have thereby not turned it into a hammer (that is, I have not turned it into itself, because it was that all along before I adopted a scientific attitude toward it). What I have done is turn it into an object of investigation. Now I investigate the hammer. I treat it the way Descartes treated the ball of wax -- as "a thing extended in space." I measure the hammer, I weigh it, I determine what elements it is composed of. I then look at a section of the hammer under an electron microscope. I note and observe the molecules of which it is composed and their structure, I note and observe the atoms, the subatomic particles, the electrons, ponder (for I can't actually observe it) their statistical cloud around the nucleus. I investigate the protons and neutrons, I calculate the atomic weight. I go even further and observe the quarks of which the larger subatomic particles are made, I go all the way down to the level of string theory and observe their characteristic vibrations. I have done all this, and yet none of it has told me what the hammer is. Indeed, the hammer is only a hammer when it has not been turned into an object of scientific investigation to be analyzed and prodded. Indeed, the hammer is most truly a hammer in my prescientific comportment toward the hammer. The less I think and ponder about the hammer, the more I actually use it in some task that has a purpose to it, do I encounter the hammer as a hammer. Hence, the most fundamental presupposition of science is its assumption -- the illusion it maintains -- that it could ever explain the world. Phenomena reveal themselves in their primordiality as being there for us, and only by being there for us do they appear as what they are. The worldview of science is actually a theoretical construction. Just listen to how scientists speak. The music we hear becomes "sound waves," it becomes "data." But this way of conceiving the world is only possible because the original phenomena have been taken out of their original context (for a context cannot exist without a situation, and to have a situation you must have a being such as a human being who is actually in a situation) and put into a highly artificial scientific context. That is, the original phenomenon has been objectified, modified, turned into an object of investigation, and thus changed in a fundamental way.
Similarly, the edifice of logic is built on a series of suppositions, for instance the basic axioms of geometry. On the basis of the basic propositions, I posit another proposition, which is also taken as valid. The "pre" in presupposition refers to a relation of logical ordering, a relation that holds between theoretical propositions, what Martin Heidegger calls "relations of founding and logical ground-laying: if this is valid, so is that." But this means that the validity even of propositions that are many generations away from the original logical axioms are dependent on the validity of the axioms upon which the edifice has been built. If, in the future, the basic axioms are found to be faulty, then it is conceivable that the conclusions built upon the basic propositions are called into question. Whether or not this turns out to be the case, it is at least theoretically possible, in which case, for all their worth, the edifice of logic is not to be taken as eternally binding. Even now, it has been determined that, depending on the overall geometry of the universe, there are scenarios in which parallel lines intersect.
Instead of writing all of the above in answer to your comment, I could also have given you a single quotation originally spoken by a general who fought for the French Revolution (only later to be executed during the Reign of Terror): "To the Jacobins, cold reason weighs infinitely more than the warmth of pity and love."
