"Superstition is to religion what astrology is to astronomy the mad daughter of a wise mother. These daughters have too long dominated the earth"

This quote by Voltaire is a comparison in between superstition and religious beliefs, and astrology and astronomy. He is saying that superstition is to religious beliefs what astrology is to astronomy; superstitious notion is the "mad child" of religious beliefs, and astrology is the "mad child" of astronomy. Voltaire is indicating that superstitious notion and astrology are unreasonable and misdirected, while religion and astronomy are sensible and logical. He is also suggesting that superstition and astrology have actually been provided too much power and impact worldwide, and that it is time for religion and astronomy to reclaim control. This quote is a suggestion that we need to take care not to be swayed by superstition and astrology, and instead count on the knowledge of religious beliefs and astronomy.