And first the Doctrine that all their Theory is grounded on, seems to me Inevident and undemonstrated, not to say precarious. - Robert Boyle

Those distinct substances, which concretes generally either afford, or are made up of, may, without very much inconvenience, be called the elements or principles of them.

That then, that I wish for, as to systems, is this, that men, in the first place, would forbear to establish any theory, till they have consulted with (though not a fully competent number of experiments, such as may afford them all the phænomena to be explicated by that theory, yet) a considerable number of experiments, in proportion to the comprehensiveness of the theory to be erected on them. And, in the next place, I would have such kind of supestructures looked upon only as temporary ones; which though they may be preferred before any others, as being the least imperfect, or, if you please, the best in their kind that we yet have, yet are they not entirely to be acquiesced in, as absolutely perfect, or uncapable of improving alterations.

I cannot conceive, how a body, destitute of understanding and sense, truly so called, can moderate and determine its own motions; especially so as to make them conformable to laws that it has no knowledge of.