ولذلك، ففي الهندسة (وهي العلم الوحيد الذي شاء الله حتى الآن أن يهبه للبشر)، يبدأ الناس بتحديد معاني ألفاظهم؛ وهذا التحديد للمعاني هو ما يسمّونه التعريفات، فيضعونها في مستهلّ حساباتهم.

“And therefore in geometry (which is the only science that it hath pleased God hitherto to bestow on mankind), men begin at settling the significations of their words; which settling of significations, they call definitions, and place them in the beginning of their reckoning.”Thomas Hobbes — The Moral and Political Works of Thomas Hobbes of Malmesbury: Never Before Collected Together : To which is Prefixed, the Author's Life, Extracted from that Said to be Written by Himself, (1750)