Reasoning is there if you simply explain that Krishna is full in 6 opulences: strength, knowledge, wealth, beauty, fame, and renunciation. No one can excel Krishna in opulence. Nobody is equal to or greater than Krishna, therefore He is God.
The word for philosophy is tattva darsana - the Bhagavad-gita recommends that one approach a spiritual master who is tattva darsana, one who has seen the truth. This is philosophy.
Letter to Mr. Prem J. Batra, 2 April, 1976