But if you know that fire is nothing more than wood whose particles are in continual agitation, and that it is only through this agitation that it arouses the sensation of heat in us; if you know also that the softness of mud only consists in a mixture of earth and water: then as these ideas are not confused and general, but distinct and particular, it will not be difficult to see that the heat of fire must harden mud; because there is nothing easier to conceive than the fact that one body can move another if, being agitated, it collides with it.