Democritus say all perception is “by convention.” What does he mean and why?

Research paper on Democritus and atomism. Make clear argument. Use primary sources, and also contrast secondary source opinions. Here are some sources one could use: Primary: Taylor, C.C.W., The Atomists: Leucippus and Democritus (Toronto: University of Toronto Press, 1999) Overview for background info: Graham, D.W. & Curd, P. (Eds.) (2008). The Oxford handbook of Presocratic philosophy Oxford University Press, Oxford. Long, A.A. (Ed.) (1999). The Cambridge companion to early Greek philosophy Cambridge University Press, Cambridge. Secondary: Andrew, Gregory, ‘Leucippus and Democritus on Like to Like and Ou Mallon’, Apeiron, 46 (2013): 446- 68. Baldes, R.W. (1978). Subjectivism and objectively true observation statements in Democritus. The Ancient World 1, 89-95. Curd, P. (2004). The legacy of Parmenides. Parmenides Publishing, Las Vegas (NV). Curd, P. (2001). Why Democritus was not a skeptic. In Essays in ancient Greek philosophy, (Ed, Preus, A.) State University of New York Press, New York, 149-169. Pancheri, L. (1975). Greek atomism and the one and the many. The Journal of the History of Philosophy 13, 139-144. Sedley, D. (1982). Two Conceptions of Vacuum. Phronesis 27(1-2), 175-193. Sedley, D. (2008). Atomism’s Eleatic roots. In Oxford handbook of Presocratic philosophy, Oxford University Press, Oxford, Taylor, C.C.W., The Atomists: Leucippus and Democritus (Toronto: University of Toronto Press, 1999)