68 Sir I S A A C N E W T O N's Book L

of her phænomena, from any ideas we are able to form of aninfinitely perfect Being. Was it not for the high reputationof the author, and of his system, it would be hardly excusableto make any remarks upon such a rhapsody. Should weallow the principles he builds on, and his method, it mustbe obvious with how weak an evidence the consequences areconnected with each other, in this visionary chain. How justa method he has taken to establish the existence and attributesof the Deity we shall not enquire, nor how far his making alltruth and falfhood dependent on the will of the Deity tendsto weaken all science and confound its principles. While hesupposes extension to constitute the complete essence of matter*he neglects solidity, and the inertia by which it resists anychange in its state of motion or rest ; which distinguish bodyfrom space. If extension be understood to be the essence ofmatter, it is a trifling proposition to affirm that all space is fullof matter, according to this definition. But still the questionwill remain, whether all space is full of that solid, moveableand resisting substance commonly called body. And as manyparts of space appear to make no sensible resistance to mo-tion, while others resist variously in proportion to the density ofthe medium diffused over them, we thence learn there is spacevoid of what is commonly called matter. The comets whichmove with equal freedom in all directions with very rapid mo-.tions, and carry along with them tails of a prodigious sizeconsisting of some highly rarisied matter, shew that the heavensare not replenished with dense fluids that admit no void. Forit is evident in experimental philosophy that the resistance offluids increases, cæteris paribus , with their density; so that allmotion would soon languish in a fluid, which, having no pores,must far surpass quick silver, or the heaviest solids, in density.Nothing is more evident, than that the force requisite to movetwo equal bodies with a given velocity, is double that whichi would