mere known to os \ than that of Spirits upon Belies , or of Bodies upon 
Spirits ; and yet moft men admire nothing but this , believing to know 
the ether: whereas he Judges , that all things being well examin'd, 
the A&ion of Bodies upon Bodies is no more conceivable, than that of 
Spirits upon Bodies. Mean while the opinion of the Aothour touch- 
ing this fubjed , is , That the union of Soul and Body confifts onely in 
this, that certain motions of the Body are followed by certain Cm. 
miens of the Soul, and, on tfie contrary, that certain Thoughts, 
of the Soul are follow'd by certain Motions of the Body. And ha- 
ving fuppofed, that Bodies arefaid to ad upon one another , when they 
eaufefome change fuitabie to Extenfion • and Spirits to ad upon one 
another, when they caufe fome change fuitabie to a Thought • he in- 
fers, that when a Body ads upon a Spirit , that cannot be by caufing 
any change of motion, of figure, or parts, as having none of all thefe & 
nor when a Spirit ads upon a Body , that cannot be by prcdu- 
ting any change of Thought, as having none: But, when this Body, or 
its motion, or figure, or other thing, depending upon its nature , can 
fee perceived by a Spirit, fo as, upon that occafion , this Spirit has 
thoughts, it had not before, it may be faid s that the Body has aded upon 
this spirit, for as much as it has caufed all the change in it, whereof it was 
capable according to its nature. 
In the Sixth , After he hath ffiew'd , what is to be underftood by 
what we call Settle and by what we call Body y he labours to make it out 3 , 
thr t we are much more affured of the Exigence of the Soul , than oT 
that of the Body , which he conceives he can prove from hence, that 
we cannot doubt, that we think , becaufe even doubting is thinking • 
but one may doubt, whether one has a body , for feveral reafons ’ 
which he alledges, and thinks fo cogent , that he concludes, it is not 
evident to him by the light of reafon , that he has a Body* But fuppo- 
fing, there be Bodies, he examines, what are the Operations, that belong* 
to the Soul , and what thefe , that belong to the Body • and laftly 3 
what thofe , tbatrefult from the Union of both: And then explains 
how all thofe operations are perform’d , and particularly, Senfation *’ 
where he fhews , that the Nerves , holding at one end to the Brain’ 
whereof they are but Allongations , and being at the other end ex- 
tended to the extremities ©f the Body • when an Objeti: comes to 
touch thofe exterior ends of the Serves, the interior ones in the 
Brain are prefently fhaken, and caufe different fenfations according 
to the diverfitie of Nerves, and the differing manner in which- 
they are fhaken. And,to fhew, that ’tis this fhaking, that caufes Senfa- 
lien j he notes, that if any thing fhakes the interior parts of the Nerves 
though the objea be abfent, the Soul has prefently the fame fen--' 
fa tions . 
