"What would naturally be there?" he snorted. "Ahead is the future; behind is the past. Those are real, the worlds of past and future. What worlds are neither past nor future, but contemporary and yet--extemporal--existing, as it were, in time parallel to our time?" I shook my head. "Idiot!" he snapped. "The conditional worlds, of course! The worlds of 'if.' Ahead are the worlds to be; behind are the worlds that were; to either side are the worlds that might have been--the worlds of 'if!'" "Eh?" I was puzzled. "Do you mean that you can see what will happen if I do such and such?" "No!" he snorted. "My machine does not reveal the past nor predict the future. It will show, as I told you, the conditional worlds. You might express it, by 'if I had done such and such, so and so would have happened.' The worlds of the subjunctive mode." "Now how the devil does it do that?" "Simple, for van Manderpootz! I use polarized light, polarized not in the horizontal or vertical planes, but in the direction of the fourth dimension--an easy matter. One uses Iceland spar under colossal pressures, that is all. And since the worlds are very thin in the direction of the fourth dimension, the thickness of a single light wave, though it be but millionths of an inch, is sufficient. A considerable improvement over time-traveling in past or future, with its impossible velocities and ridiculous distances!" "But--are those--worlds of 'if'--real?" "Real? What is real? They are real, perhaps, in the sense that two is a real number as opposed to √-2, which is imaginary. They are the worlds that would have been _if_-- Do you see?" I nodded. "Dimly. You could see, for instance, what New York would have been like if England had won the Revolution instead of the Colonies." "That's the principle, true enough, but you couldn't see that on the machine. Part of it, you see, is a Horsten psychomat (stolen from one of my ideas, by the way) and you, the user, become part of the device. Your own mind is necessary to furnish the background. For instance, if George Washington could have used the mechanism after the signing of peace, he could have seen what you suggest. We can't. You can't even see what would have happened if I hadn't invented the thing, but _I_ can. Do you understand?" "Of course. You mean the background has to rest in the past experiences of the user." "You're growing brilliant," he scoffed. "Yes. The device will show ten hours of what would have happened _if_--condensed, of course, as in a movie, to half an hour's actual time." "Say, that sounds interesting!" "You'd like to see it? Is there anything you'd like to find out? Any choice you'd alter?" "I'll say--a thousand of 'em. I'd like to know what would have happened if I'd sold out my stocks in 2009 instead of '10. I was a millionaire in my own right then, but I was a little--well, a little late in liquidating." "As usual," remarked van Manderpootz. "Let's go over to the laboratory then."