By the time of Francis Bacon and the scientific revolution, newly emerging scientific disciplines acquired a method of systematic empirical induction based upon experimental observations. At this point, astrology and astronomy began to diverge; astronomy became one of the central sciences, while astrology was increasingly viewed as an occult science or superstition by natural scientists. For example, Christiaan Huygens wrote in his Cosmotheoros: "And as for the Judicial Astrology, that pretends to foretel what is to come, it is such a ridiculous, and oftentimes mischievous Folly, that I do not think it fit to be so much as named." This separation accelerated through the eighteenth and nineteenth centuries. Contemporary scientists such as Richard Dawkins and Stephen Hawking regard astrology as unscientific, and those such as Andrew Fraknoi of the Astronomical Society of the Pacific have labeled it a pseudoscience. In 1975, the American Humanist Association characterized those who have faith in astrology as doing so "in spite of the fact that there is no verified scientific basis for their beliefs, and indeed that there is strong evidence to the contrary".Astronomer Carl Sagan was unwilling to sign the statement, not because he felt astrology was valid, but because he found the statement's tone authoritarian. Sagan stated that he would instead have been willing to sign a statement describing and refuting the principal tenets of astrological belief, which he believed would have been more persuasive and would have produced less controversy than the circulated statement.