Theory of science - Pre-Reflection

The relation mind-body has always been exploited by philosophy, from Plato's "Allegory of the Cave" which firstly highlighted the gap between what ideas and their representations are and how the holy truth is not always well accepted.

The true skepticism moved its first steps from René Descartes defining the distance between the "res cogitans" and "res extensa", hence what things actually are and what our perceptions of them are, casting a shadow on what we could know and by the quote "cogito, ergo sum" reducing this range exclusively to the "me as myself".

Russell's "sense-data" -our sensation of the physical objects surrounding us, collectively composing the matter- are more similar to Kant's "phenomenons" which are completely opposed to their antithesis "noumenons", hence those postulates that are directly knowable without the use of senses.

The most clarifying example in Russell's "Problems of Philosophy"is the one about a coin;

In our head a coin is round shaped, bronze coloured, it has a certain weight, but actually observing a real coin we might notice that it is more elliptical shaped unless we do not have it in a precise straight forward position and its colour may differ according on how the light hits its surface, and so on.

Likewise even the scientific empirical cartesian method is fallacious because results from an experiment are sense-data and so being they are proposed to be the common rule, the very likely truth, but still they are only "propositions".

In this way we are "proposing" in the common sense to use this sentence as naturally and logically true due to its fairly good evidence.

Once the threshold in the number of those who found this sentence true is overstepped, a proposition becomes a "statement of fact", hence it is conventionally assumed as truth.

In humans' mind the earth was flat until Colombo, Vespucci, Magellano and Caboto proved there was no edge with monsters and storms casting adventurers in the outer space.

Thus there are two different way to grasp the knowledge of things, or rather "by acquaintance" and "by description".

As we saw sense-data are a tool to acquire knowledge by acquaintance, empirically inferred by experience and completely independent from any knowledge of idea.

Sight, sound, smell, taste and touch sensations describe us the direct appearance of the physical object in front of us thus they are not giving us the concept of "physical object".

The knowledge of "physical object" has been acquired by description as the entity that rouse this set of sense-data when I am exposed to it, this knowledge is typically what we have been told and taught without any direct experience on it.

Knowledge by description is then further exploited defining the definite description, essentially referring to an object among others, for instance 'the man with the iron mask' gives us much more information than the sole 'a man' which is an ambiguous description.

But there must be other kinds of knowledge by acquaintance since if sense-data would be the only example, we could "only know what is now present to our senses: we could not know anything about the past--not even that there was a past--nor could we know any truths about our sense-data".

In the final analysis we can state there are two different extensions beyond sense-data, namely knowledge by memory and by introspection allowing us to be aware of a former experience and to be aware of our awareness.

The theory of truth virtually ensures the possibility for some facts to be completely true, supplies opportunity of infallibility.
The great question in this essay is in the end how discern between statements of facts, a conventional belief, and and a true belief?
In Russell's critique against traditional epistemology we can firstly notice he distances himself from the Aristotelian syllogism since even if the premisses and the conclusion are true the conclusion does not follow from the premisses;

For instance saying "all Greeks are men" and "Socrates was a man" we can invalidly conclude that "Socrates was a Greek".
Knowledge acquired by intuition and derivative processes does not give us a reliable belief, but thankfully premisses are not our only source of knowledge.

The main critique Russell move is against those philosophers who profess to be able to prove "a priori metaphysical thesis" such as religions, rationality of universe and so on.

The hope for finding reason to believe these thesis is in Russell's opinion vain basically and simply for the fact that assuming logically the existence or non-existence of such and such things could not success in a critical scrutiny.
Hegelian idealism gives us the hint that every part of a whole is fragmentary and subsistence free without any relation with the left over part.
Barring the absolute idea, all other lower ideas are somehow deficient in their description of reality, the full understanding of an object’s nature depends on its relation to another and the resulting vicious circle prevents us from the knowledge about the truth, unless we do not know every relation a thing establishes to every other thing in the universe.
Therefore truthful essence of things is a chimaera, it is relative and context dependent and so being fallacious in supplying a scientific truth, we still deal with beliefs and regardless their collectively agreement still they remain mere beliefs.