Is not that enough, said she; for an opinion that is merely probable? You would be astonished, answered I, if I told you the word probable was too modest for the occasion. Is it merely probable that Alexander has been in existence? No, you consider it certain; and what is the ground of your certainty? Is it not that you have had every proof that such a subject requires, and that no circumstance leads you to doubt the fact? You have never seen Alexander, nor have you any mathematical demonstration of his existence. What would you say if this were the case with respect to the inhabitants of the planets? We cannot shew them to you, nor can you require us to demonstrate their being, in a mathematical way; but you have all the evidence that can be desired: the entire resemblance between the planets and the inhabited earth; the impossibility of imagining any other use for which they could be created; the fruitfulness and magnificence of nature; the attention she seems to have paid to the wants of their inhabitants, such as giving moons to those planets that were very remote from the sun, and the greatest number of moons to the most distant: and it is an important consideration that every thing is on that side of the question, without any objections to counterbalance it; you cannot for a moment doubt unless you resume the vulgar mode of seeing and thinking. In fact it is impossible to have more evidence, and evidence of a more determinate kind; how then can you treat this opinion as a mere probability? But do you think, said she, I can feel as certain that the planets are inhabited, as that Alexander has been in existence? By no means, I replied; for although, on the subject we are speaking of we have as many proofs as in our situation we can receive, yet these proofs are not numerous. I protest, exclaimed she, I'll renounce these planetary inhabitants, for I don't know whether to believe there are any or not--it is not certain, yet it is more than possible--I am quite perplexed. Do not be discouraged, madam, I replied. Clocks that are made in the most common manner shew the hour; those only that are made with more exquisite art, indicate the minutes; in like manner common minds see a great difference between probability and absolute certainty; but it is only superior understandings that ascertain the degrees of certainty or of probability, and who, if I may use the expression, can tell the minutes as well as the hours. Place the inhabitants of the planets a little below Alexander in point of certainty, but above a vast number of historical relations which are not entirely proved; I think that is their proper place. I love order, said she, you do me a kindness in giving arrangement to my ideas: why did you not do this before? Because, answered I, whether you attribute to this idea a little more, or a little less certainty than it possesses is not of much consequence. I am certain you do not feel