Bernard Nieuwentijt, Nieuwentijdt, or Nieuwentyt (10 August 1654, West-Graftdijk, North Holland – 30 May 1718, Purmerend) was a Dutch philosopher, mathematician, physician, magistrate, mayor (of Purmerend), and theologian. As a philosopher, he was a follower of Descartes and an opponent of Spinoza. In 1695 he was involved in a controversy over the foundations of infinitesimal calculus with Leibniz.
He wrote several books (in Dutch) including his chief work Het regt gebruik der werelt beschouwingen, ter overtuiginge van ongodisten en ongelovigen [The True Use of World-Concepts] (1715), which argued for the existence of God and attacked Spinoza. It went through several editions (1715, 1717, 1720, 1725, 1730, 1740) published by Joannes Pauli, and was translated into English as The religious philosopher, or the right use of contemplating the works of the Creator (1718) and into French as De l'existence de Dieu démontrée par les merveilles de la nature, ou traité téléologique dirigé contre la doctrine de Spinoza par un médecin hollandais. Voltaire owned a copy of this book, and it was an influence on William Paley.
Nieuwentyt's posthumously published Gronden van zekerheid [Fundaments of Certitude, or the Right Method of Mathematicians in the Ideal as well as the Real] (1720) argued Spinoza's 'geometrical method' was not the proper 'experimental method' of science. The work also contains a critique of the ontological argument similar to a later critique by Kant.
- Het regt gebruik der werelt beschouwingen, ter overtuiginge van ongodisten en ongelovigen, Amsterdam, 1715
- Gronden van zekerheid, 1720
- Beth, Evert W (1950). "Critical Epochs in the Development of the Theory of Science". British Journal for the Philosophy of Science. 1 (1): 27–42.
- Jonathan Israel, Enlightenment Contested, p. 385–6