There are three kinds of Scriptures. First type do not describe events but spiritual experiences that occur in inner subjective space and often belong to what is called as the fourth or simply other dimensions than the material world. The Vedas belong to this class of Scriptures.
The only way to verify them is to engage in the practice and undertake the inner journey as they advice and see if there is any truth in them or not. However if one is unwilling to try out the experiment for whatever reasons then it is best to say that ‘I don’t know whether they are true or not.’ But to say without trying that it is imagination is a dishonest and unscientific statement much like saying that all talk of landing on the moon or Mars is humbug.
There is another kind of Scripture that gives us the path to rise out of our ordinary mundane existence and lead a nobler, higher, better, diviner life. The Upanishads and the Gita fall in this category.
Here evidence means whether the path they have shown and the claims they make is true or not. Here again the best way is to try it if one has the aspiration to discover a higher, nobler, diviner way of life. In that case one starts with faith and sees the results through practice. Or else one tries to first find if there are people who have undertaken the practice and got the results. Fortunately there are plenty who have had the results over number of millennium. That is how the knowledge has survived and developed over generations through the Guru Shishya parampara as in any field of practice. Here again to say that one does not believe in them is as good or as bad as saying that one believes in them. This class of Scriptures are unique to Sanatan Dharma and are called yoga shastras. They are not so much to be believed as to be lived.
It is the third category known as the Puranas and Itihasas that the question of evidence as you mention arises. As to the Itihasas, that is the Ramayana and the Mahabharata, I have given a detailed talk about the authenticity of these two great events in history. Certainly there is here, as well as in the Puranas, the use of symbols and imagery (not imagination) to highlight certain aspects such as the ten heads of Ravana and suchlike. But this is so because the purpose of these scriptures is not so much as to give a datewise historical account of purely physical events (if at all such a thing were possible!) but to awaken us to the deeper, higher, subtler truths of existence; to instruct us about the many criss-cross layers of forces that weave our life and fate; above all to present living example of characters that have moulded generations to come. Their value is not to be assessed so much by examining whether these events actually took place or not but by observing how they have impacted and continue to influence many human beings to become better and lead a nobler life. They provide archetypes, moulds of human personalities that always exist in some form or the other and show us where their actions lead them so that we can make better and informed choices about our own life. It is of course upto each one of us to accept these examples to remould our lives into something higher or to leave them as a story that does not inspire enough.
Affectionately,
Alok Da
