How much this is the case in the greatest part of disputes that men are engaged so hotly in, I shall perhaps have an occasion in another place to take notice.  Let us only here consider a little more exactly the fore-mentioned instance of the word gold, and we shall see how hard it is precisely to determine its signification.  I think all agree to make it stand for a body of a certain yellow shining colour; which being the idea to which children have annexed that name, the shining yellow part of a peacock’s tail is properly to them gold.  Others finding fusibility joined with that yellow colour in certain parcels of matter, make of that combination a complex idea to which they give the name gold, to denote a sort of substances; and so exclude from being gold all such yellow shining bodies as by fire will be reduced to ashes; and admit to be of that species, or to be comprehended under that name gold, only such substances as having that shining yellow colour, will by fire be reduced to fusion, and not to ashes.  Another, by the same reason, adds the weight, which, being a quality as straightly joined with that colour as its fusibility, he thinks has the same reason to be joined in its idea, and to be signified by its name:  and therefore the other made up of body, of such a colour and fusibility, to be imperfect; and so on of all the rest:  wherein no one can show a reason why some of the inseparable qualities, that are always united in nature, should be put into the nominal essence, and others left out, or why the word gold, signifying that sort of body the ring on his finger is made of, should determine that sort rather by its colour, weight, and fusibility, than by its colour, weight, and solubility in aqua regia:  since the dissolving it by that liquor is as inseparable from it as the fusion by fire, and they are both of them nothing but the relation which that substance has to two other bodies, which have a power to operate differently upon it.  For by what right is it that fusibility comes to be a part of the essence signified by the word gold, and solubility but a property of it?  Or why is its colour part of the essence, and its malleableness but a property?  That which I mean is this, That these being all but properties, depending on its real constitution, and nothing but powers, either active or passive, in reference to other bodies, no one has authority to determine the signification of the word gold (as referred to such a body existing in nature) more to one collection of ideas to be found in that body than to another:  whereby the signification of that name must unavoidably be very uncertain.  Since, as has been said, several people observe several properties in the same substance; and I think I may say nobody all.  And therefore we have but very imperfect descriptions of things, and words have very uncertain significations.

18.  The Names of simple Ideas the least doubtful.