Notices respecting New Books. 331 
therefore here assumed, as a first principle, by universal consent, 
that phantoms of colour are but ‘ a species of thought.’ 
“3. With this only settled principle, it has ever been. one of 
the greatest problems in philosophy to discover the mature and 
place of those outlines, that are seen as it were surrounding the 
phantoms of colours, and to which we give the appellation of 
visible figure.— There now exist only two opinions concerning 
this matter: perceived figures are either the real identical forms 
of external and distant bodies ; ; or, they are actually the forms 
of our own sensations, which, if so, do not show, but only imdi- 
cate, some unknown external cause. The highest authorities 
of the last century have divided upon this point: and the literary 
public, impressed by the untoward character of the schism, ap- 
pear to consider all proof, or foundation on the subject, as a de- 
sideratum utterly hopeless. Such is the discouraging introduc- 
tion to the following principles. 
“* OF THE POSSIBLE CASES OF VISION, 
_ © All the possible cases, or accidents, of primary vision. fall 
under fowr general facts, or laws. 
“* Bach of these four laws is also an axiom: its truth does 
not depend upon the laws of Nature, but on the law of thought 3 
since, the moment it is apprehended, we discern ‘that, its con- 
trary isimpossible. This forms the most striking and important: 
character of the phenomena of vigion. 
. ~ Two of the laws of vision are wnformative, either of any 
figure, or of any element of figure. 
_ © The other two lays are formative, either of some figure, or 
of some element of figure. 
“ First Law.—Unformative.. 
~ © Prop. No one uniform sensation of colour can ever be ac= 
companied by a percepeen of any visible figure, any line, or any 
point. 
Inst. If the eye traverse the unclouded heaven, or if itiskim 
the surface of the sea, we shall undergo a uniform sensation of 
one colour ; and here it is self-evidently impossible we should, 
ever perceive any visible figure, any line, or any point, so long as 
the sight keep within the field of this one colour. 
_ © It is plainly as impossibleito conceive a visible line, without 
calling up some second colour, as it is to conceive a boundary to 
an infinite surface : for, any colour we perceive, must be abso- 
hitely without end, if it be not terminated by our view of some 
second, colour. 
“ Second Law.—Formative. 
© Prop, When any two unblended sensations of colours are 
felt 
