One view of reason - the perspective of critique - posits that reason is fundamentally posterior to desire: reason distorts desire, captures it, represses it, structures it, or rather is this very distortion. By the same token, reason rationalizes on behalf of desire. Reason itself is distorted by the desire in the name of which it has been summoned. By these lights, reason should not be trusted.
An opposing view - or rather the establishment view that the above view opposes - is that reason is prior. Desire is inherently pathological, unless it is guided and transfigured by rational cognition - which has either a divine or quasi-divine source. Here reason is self-sustaining.
Endeavor supposes a middle road between these: reason has both a Hyperborean and a Transcendental mode.