  The fact that Descartes offered mechanistic explanations for many features of nature does not mean that his explanations were successful. Indeed, his followers and detractors debated the success of his various proposals for nearly a century after his death. His accounts of magnetism and gravity were challenged. Leibniz challenged the coherence of Descartes' laws of motion and impact. Newton offered his own laws of motion and an inverse square law of gravitational attraction. His account of orbital planetary motions replaced Descartes' vortexes. Others struggled to make Descartes' physiology work. There were also deeper challenges. Some wondered whether Descartes could actually explain how his infinitely divisible matter could coalesce into solid bodies. Why shouldn't collections of particles act like whiffs of smoke, that separate upon contact with large particles? Indeed, how do particles themselves cohere?