482 Mr. Brcuzxo on Systems and Methods 
and producing by certain laws of generation others like itself: 
whereas all that logicians have meant, is a number of objects 
bearing a certain resemblance to one another, and on that ac- 
count denominated by a single appellation, which may be em- 
ployed to express any one of them. This term is the creature 
of art, to help us up the first step of generalization. By its as- 
sistance we propose to reason upon all the individuals conform- 
ing to the law we have laid down, as safely as we can do of any 
one of them. "There is this inconvenience attending the use 
of it by naturalists, that it assumes as a fact, that which in the 
present state of science is in many cases a fit subject of in- 
quiry ; namely, that species, according to our definition, do exist 
throughout nature. It is too convenient a term to be dispensed 
with, even as an assumption; only care should be taken that 
we do not accept the abstract term for the fact. 
It might, for instance, be proposed as a legitimate question, 
whether the species of some familiar genera, such as Rosa, 
Rubus, Saxifraga, do not run into one another by imperceptible 
shades, unappreciable by human sense, in the same manner as 
certain genera melt and intermingle their characters, so as to 
render it impossible to circumscribe them. Indeed, the extent 
to which species-making has been carried in modern times, al- 
most leads to this conclusion. Visible and palpable distinctions 
are in many cases no longer relied on ; and there are many acute 
naturalists, who, without bringing the subject to the test of experi- 
ment, are content to rely on those empirical characters, which can 
only be perceived by long and familiar experience, and cannot 
be described by words. The truth is, that all sensible objects 
have characters which leave impressions upon the mind, without 
our being capable of embodying them in language. Weare all 
aware of this when we speak of tastes, and tints, and the counte- 
nances of our friends. Every-body perceives them, yet nobody 
can 
