Kekulé had become practiced in receiving and developing helpful images in this way. When he described the roots of his scientific creativity in the Benzolfest in his honor in 1890, Kekulé told his audience, “Let us learn to dream, gentlemen, then perhaps we shall find the truth.” He added the salutary caution, “But let us beware of publishing our dreams till they have been tested by the waking understanding.”
The images that came to Kekulé would have been meaningless, in terms of chemistry, to someone who did not have a scientific mind that had long been working on the problems whose solutions they revealed. The imagery might have sent an artist off to paint, or sent someone with an interest in myth off to study the symbol of the Ouroboros in the ancient world and in alchemy.
When Kekulé urged his audience to “dream”, he was surely not talking exclusively, or primarily, about what happens in sleep. He was talking about developing the ability to enter a state of relaxed attention in which ideas take form and interact as images.