 Here is one way of seeing how this might work: If I conceive of a world in which everyone by nature must try to deceive people any time this will get them what they want, I am conceiving of a world in which no practice of giving one’s word could ever arise and, because this is a law of nature, we can assume that it is widely known that no such practice could exist. So I am conceiving of a world in which everyone knows that no practice of giving one’s word exists. My maxim, however, is to make a deceptive promise in order to get needed money. And it is a necessary means of doing this that a practice of taking the word of others exists, so that someone might take my word and I take advantage of their doing so. Thus, in trying to conceive of my maxim in a world in which no one ever takes anyone’s word in such circumstances, and knows this about one another, I am trying to conceive of this: A world in which no practice of giving one’s word exists, but also, at the very same time, a world in which just such a practice does exist, for me to make use of in my maxim. It is a world containing my promise and a world in which there can be no promises. Hence, it is inconceivable that I could sincerely act on my maxim in a world in which my maxim is a universal law of nature. Since it is inconceivable that these two things could exist together, I am forbidden ever to act on the maxim of lying to get money.