Did our ancestors go peeping about with dark lanterns, and do we walk at our ease in broad sunshine? Where is the manifestation of our light? By what symptoms do you recognise it? What are its signs, its tokens, its symptoms, its symbols, its categories, its conditions? What is it, and why? How, where, when is it to be seen, felt, and understood? What do we see by it which our ancestors saw not, and which at the same time is worth seeing?