It is Nietzsche who shed the most light on the relationship between knowledge and temperament, teaching us that neurotic moods beget neurotic forms of knowledge, that an unstable temperament gives birth to troubled categories and concepts. The infamous German iconoclast was one of the first to suggest that knowledge was not objective but rather evolves differently based on the underlying mood that conditioned the emergence of that knowledge. In other words, knowledge is cultural and circumstantial.
Societies have underlying temperaments as well as individuals. So the knowledge I apply to the world is informed from two directions: the culture through which I was socialized and the idiosyncratic milieu that is my emotional constellation (although the latter is largely shaped by the former). My take on "reality" is doubly distorted.
There is no "view from nowhere" that could establish eternally a direct correspondence between the world and the words we use to come to terms with it. Not even science will ever reach "perfect" knowledge, because the idea that we could have perfect knowledge denies the truth that the universe is in flux; the world is flow. The idea of an eternal, objective knowledge is an idea of a static, stationary, un-evolving universe, one that slaps in the face of our experience of history, science, and culture.
So if moods and temperaments of the day dictate knowledge, then all we must do is change our mood! As if it's an easy thing to do. Moods - especially cultural ones - are deeply embedded and often appear totally natural (if they even "appear" at all!). The hardest thing to do sometimes is to create space between one's perspective and the temperaments that pervade the social and psychological worlds. Cynicism might be, in our day, the foe with the longest fangs, salivating over the young and under-spirited.
The practice of yoga and meditation (and they are eventually the same) is a practice of creating that space in which moods appear as what they are: transient and changeable. A sober-minded yet inspired and enchanted temperament becomes something that, by continuously bringing it forth as an intention, works to re-shape old and forge entirely new categories through which to look upon the world in a more sacred light.