NOTES AND ILLUSTRATIONS. 255 
presupposed. When, therefore, he affirms labour itself to 
be a common measure of value, he makes a transition to 
the other sense of the phrase, and means, that when the 
quantities of labour respectively required to produce com- 
modities are known, their values in relation to each other 
are thereby determined. 
This distinction, constantly borne in mind, would, I am 
persuaded, throw great light upon the obscurity which 
clouds many discussions in political economy, and clearly 
show the source whence it has proceeded. 
THE END.