The factors left out of the Ricardian equation are falling wages and idle capacity.

Labour, like all other things which are purchased and sold... has its natural and its market price.

The wheat bought by a farmer to sow is comparatively a fixed capital to the wheat purchased by a baker to make into loaves.

If I discover a manure which will enable me to make a piece of land produce 20 per cent more corn, I may withdraw at least a portion of my capital from the most unproductive part of my farm.

The price of corn will naturally rise with the difficulty of producing the last portions of it.

...I wish that I may never think the smiles of the great and powerful a sufficient inducement to turn aside from the straight path of honesty and the convictions of my own mind.

It appears to me that one great cause of our difference in opinion on subjects which we often discuss is that you have always in mind the immediate and temporary effects of particular changes, whereas I put these effects quite aside, and fix my whole attention on the long-term effects that will result from them.