Vichāra[1] (Pāli: vicāra) in Indian philosophy means deliberation; it is the faculty of discrimination that discerns the Real, Brahman, from the unreal.
Taittiriya Upanishad tells us:- that all should know Brahman as existing in the intellect in which, Shankara explains, are hidden – a) 'knowledge', b) 'the knowable' and c) 'the knower', as also enjoyment and liberation.
[5] Vedanta ( the eternal path) activates vichāra ('inquiry') to increase viveka ('discrimination') to deconstruct vivarta ('false superimposition') to destroy vasanas ('root desires') and thus establish vairagya ('detachment'), become a vidvan ('wise person') and attain vijnana ('self-realization'); these factors combined facilitate in the human aspiration and Divine Dispensation working harmoniously together.
In Vedanta, rational reasoning is vichāra that discriminates between the real and the unreal; it dispels prejudices such as irrational doubts, preconceived notions/ideas and personal sentiments to scrutinize the meaning of Truth.
Shankara in his commentary on the Mandukya Upanishad explains that Vedantic reasoning reveals the essential meaning of scriptural statement in the context of its goal, proves the logical untenability of all contrary concepts so as to establish the intelligibility of non-dualism and expose the mutually contradictory nature of dualistic views about Reality.