"Practice without theory is blind. Theory without practice is sterile." - Karl Marx
"No coarser insult, no baser aspersion, can be thrown against the workers than the remarks: 'Theoretic controversies are only for academicians.'" - Rosa Luxemburg
"Moral—Don't be "practical" in politics. To be practical in that sense means that you have schooled yourself to think along the lines, and in the grooves which those who rob you would desire you to think." - James Connolly