“What do we know,” he had said, “of the world and the universe about us? Our means of receiving impressions are absurdly few, and our notions of surrounding objects infinitely narrow. We see things only as we are constructed to see them, and can gain no idea of their absolute nature. With five feeble senses we pretend to comprehend the boundlessly complex cosmos, yet other beings with a wider, stronger, or different range of senses might not only see very differently the things we see, but might see and study whole worlds of matter, energy, and life which lie close at hand yet can never be detected with the senses we have. I have always believed that such strange, inaccessible worlds exist at our very elbows, and now I believe I have found a way to break down the barriers.”

“With five feeble senses we pretend to comprehend the boundlessly complex cosmos, yet other beings with wider, stronger, or different range of senses might not only see very differently the things we see, but might see and study whole worlds of matter, energy, and life which lie close at hand yet can never be detected with the senses we have.”

“although we very clearly see the sun, we ought not therefore to determine that it is only of the size which our sense of sight presents; and we may very distinctly imagine the head of a lion joined to the body of a goat, without being therefore shut up to the conclusion that a chimaera exists; for it is not a dictate of reason that what we thus see or imagine is in reality existent; but it plainly tells us that all our ideas or notions contain in them some truth.”

“All we have to believe with is our senses, the tools we use to perceive the world: our sight, our touch, our memory. If they lie to us, then nothing can be trusted. And even if we do not believe, then still we cannot travel in any other way than the road our senses show us; and we must walk that road to the end.”

“You perceive the world with your five senses. When your mind perceives the world, then the world exists before you. But if we are born without any senses, then how could we perceive the world except as a dream in our minds? But then...dreams often seem as real as the world we see now. Look...If I touch you with this hand, I can remember touching you, but I can't ever prove I did. If reality is nothing more than what is in our mind, then what is the difference between this world and a dream?”

“The human eye has to be one of the cruelest tricks nature ever pulled. We can see a tiny, cone-shaped area of light right in front of our faces, restricted to a very narrow band of the electromagnetic spectrum. We can’t see around walls, we can’t see heat or cold, we can’t see electricity or radio signals, we can’t see at a distance. It is a sense so limited that we might as well not have it, yet we have evolved to depend so heavily on it as a species that all other perception has atrophied. We have wound up with the utterly mad and often fatal delusion that if we can’t see something, it doesn’t exist. Virtually all of civilization’s failures can be traced back to that one ominous sentence: ‘I’ll believe it when I see it.’ We can’t even convince the public that global warming is dangerous. Why? Because carbon dioxide happens to be invisible.”