Philosophical training as the taming/tempering of the feeling of being convinced* by an argument:
Through a long process of repeatedly studying arguments, feeling convinced by them and then each time realising that there is an equally convincing (and rational) counter-argument, the threshold for being convinced gradually rises and one feels less and less convinced by rational arguments. At the end, only a perfect argument [, which has the character of direct, visual understanding,] elicits the feeling of being convinced.
That is maybe the central training/disciplining of rational thinking, and the central learning technique of philosophical training. It disciplines rationality in that it teaches one the limitations and pitfalls of rationality – of analysis by [logical] argumentation – it balances the radical ambitions of abstract analysis, instilling humility into the thinker who wants to attempt abstraction of the world – especially by means of argumentative analysis of ideas.
This practice leads to a gradual increase of the degree to which one is intuitively careful, skeptical and critical toward the tools of logical/abstract/rational analysis/argumentation themselves – a kind of meta-criticism or meta-criticalness. And, importantly, this resulting reflective skeptical stance toward rationalistic, abstract criticism somewhat ironically has the effect of gradually opening the mind, as it makes one slower to dismiss an idea that one has counter-arguments to! This is maybe the dialectic extreme/final limit/end of rationality.
– [Paranoid/simplistic] conspiracy theorists lack this training & ability, whilst also being very open-minded [by natural pre-disposition], and thus their open minds are too easily and quickly filled/satisfied by [non-perfect] argumentation (maybe argumentation that is critical of some mainstream position and that suggests some non-mainstream idea) – their minds are quickly, suddenly filled by a huge, un-tempered feeling of convincedness – a feeling they aren’t trained to handle and have no reason to question.