Dr S Radhakrishnan explains the true knowledge of God by quoting from the Upanishads and the Bhagavad Gita in an article in the book 'Our Heritage.'
True religion consists in an insight into the first principle of God, knowledge, personal knowledge of God, not merely a dogmatic statement about Him, not merely what you hear from other people, but seeing Him face to face; that constitutes the essential basis of religion.
The Upanishad tells us that what we should know is a knowledge of God, not an intellectual knowledge, but an illumined personal experience of the Supreme. There is a world of difference between those who say ‘
There are many people who go about saying God exists, but that knowledge of the existence of God is indirect, it is not personal, it is merely theoretical and borrowed knowledge. Those who say, I have felt the reality of God in the pulse of my being, I have felt him in my nerves and my bones, I know Him as deeply as I know myself that is true knowledge of God: what the Gita calls brahma samsparsa.
Dr S Radhakrishnan
Source: Excerpts from Our heritage – S. Radhakrishnan