There are truths that are true only in a certain line, in a certain direction, under certain circumstances, and for certain times — those that are founded on the institutions of the times. There are other truths which are based on the nature of man himself, and which must endure so long as man himself endures. These are the truths that alone can be universal, and in spite of all the changes that have come to India, as to our social surroundings, our methods of dress, our manner of eating, our modes of worship — these universal truths of the Shrutis, the marvellous Vedantic ideas, stand out in their own sublimity, immovable, unvanquishable, deathless, and immortal. Yet the germs of all the ideas that were developed in the Upanishads had been taught already in the Karma Kanda. The idea of the cosmos which all sects of Vedantists had to take for granted, the psychology which has formed the common basis of all the Indian schools of thought, had there been worked out already and presented before the world.(III, 395)
This is the part of the lecture that Swamiji delivered at Lahore on 12th November 1897. We find here an exhaustive description of the two worlds, external and internal, which were analysed by man eager to get answers for all the deep problems that confronted him. Swamiji goes on to describe how the analysis of the internal world was taken up by the Indian mind which finally led to the discovery of the ultimate undivided One Truth.