I confess that I have no innate feeling for countable and mass nouns. I've been told that even toddlers can tell the difference between objects and substances, that it's hardwired in our minds. Yet this hardwiring is powerless to explain the difference between fruit and vegetables. The Chinese treat all of their nouns as mass nouns and just look at them going and going: one billion persons of people working together to increase one piece of GDP. We can do it, too. It has been done:
...[pea] adopted into English as the noun pease (plural peasen), as in pease pudding. However, by analogy with other plurals ending in -s, speakers began construing pease as a plural and constructing the singular form by dropping the "s", giving the term "pea".
...17c., false singular from M.E. pease (pl. pesen), which was both single and collective (e.g. wheat, corn) but was mistaken for a plural, from O.E. pise (W.Saxon), piose (Mercian) "pea," from L.L. pisa, variant of L. pisum "pea," from Gk. pison.
http://www.etymonline.com/index.php?l=p&p=8 As recently as 1889, the purists were still fighting over pease:
...According to the 1889 Century Unabridged Dictionary, pea is "A modern form, assumed as singular of the supposed plural pease. The dictionary attempted to guide grammar into reserving pea for a single seed, "...but when used collectively the old singular pease is properly used, as a 'bushel of pease'..."
but the battle was lost. So it is possible. I know exactly where to start. I have a dream.
One day I wake up and have a toast for breakfast...