On Presupposition

It has been said that all of humanity begins thought with presuppositions. Whenever someone begins to think about a certain topic, they do so with a particular bias of some sort. For instance, if one begins to think about the existence of earth and how it came to be, chances are they will presume either the idea of creation or the idea of evolution to be true, seeing as how these are the two dominant explanations. Having this presumption makes discovering supportive proofs for it easier to find regardless of the slant of the person.
Said another way, if you already believe in something (creation or evolution), you will look specifically for the “proof” to support your point of view and use it as evidence for your position.
It seems to me that the word presupposition (supposition would do just as well) itself means belief or at least pre-belief. If you start with a supposition of something, you suppose it to be true beforehand. Why not just say you believe this and be done with it?

There is a problem with saying that all human thought begins with presupposition.
What I mean is, children don’t have pre-existing suppositions of any topic of thought. They and we all begin with an innocent mind. It is only after society, religion, our parents and extended family etc.. distort this innocence into their own conceptions do children lose the innocence of ideas and pure thought. Since we all began as children, it follows that none of us began with supposition. As adults, we might very well do so, but that is simply because we have inherited the suppositions of our parents/teachers/friends; they are not our own.
What we decide to do with those inheritances is a decision we as adults have to make, but as children we do and think what we see and are told to.
We teach our children to have our stances on such things as religion, politics and socially acceptable behavior. If we teach our children to be brave enough to think for themselves and how to do so, will we usurp indoctrination and free our children to be more humane.
Starting with a supposition does not however mean that any “proof” found is false. It only ensures that the proof was more easily discovered because of deductive reasoning or intuition.
Charles Darwin set off aboard the H.M.S. Beagle in 1831 with no intention of finding proof of his then unrealized theory of natural selection.
It was in fact the other way around, he observed what was there and formulated his theory afterwards, which he laid down in “On the Origin of Species” (1859) much later.
He did not believe that evolution through natural selection was true in advance of his trip. He observed it in practice during his voyage. His training for the clergy would most certainly not have put the idea in his mind.
It is quite fortunate for us that he chose a different career path.
The finches he studied on The Galapagos Islands were as unknown to him as they were to Noah until of course he found them and observed the differences in the shapes of their beaks. These differences he noted were, from island to island, specifically acclimated to harvesting the particular foods available on each island.
He did not have any idea that this arrangement of the physical attributes of the local wildlife on remote islands in the Pacific Ocean would exist.
The situation he observed led him to his eventual thoughts on natural selection, not the other way around.

Scientists probably do as a general rule start out with one supposition though, that being, the truth is discoverable, and worth the effort.

Evolution through natural selection is a concept, which does not need to or can be proven, due to the definition of a Theory. Creation doesn’t even qualify as a theory by definition.
I refer you to an interesting article that I believe might shed some light on the subject.

All we can do is test a theory.
Theories by definition can never be “proven”, they can only stand up repeatedly to tests, or fail to do so. If they stand up, they are accepted as true until such time as they fail.
I will happily concede that such a time may come for the theory of evolution, but I personally don’t think it will, considering the theory has survived intact since 1859.
Creation is untestable.
This disqualifies it from the discussion of viable theories for existence. A theory has to be testable, in order to see if it is rigorous enough to withstand doubt.

The scientific theory of evolution through natural selection is completely testable. It has been tested over and over again. It may be disproven someday, but up until now it has not been and this only testifies to it's resilience to scrutiny. Creation, however, can easily be debunked by simply thinking of all we know now, that the authors of the bible did not know.

Creation is the fantastically superstitious myth of scientifically ignorant Arabic peasants from a few thousand years ago for which (to quote Sam Harris) a wheelbarrow would have constituted emerging technology. That the world at large can buy into this children’s story is laughable.