The object of this paper is to demonstrate the philological relation between justice, law and equality in ancient Greek or, that is the same, the philosophical relation between ethics, politics and economics. Actually it is interesting to examine the etymology of the word dikē which derives from the Sanskrit diś-(dik) and it refers more than to the generic idea of the «straight line» to the specific and astronomical concept of the «horizon (or skyline)», the apparent line that separates the cosmos (...) into two equal parts, the earth from the sky, meaning the same idea of equality which should be a rule of just law and ethical perfection. Moreover, according to my hypothesis Plato may have used the analogy of the horizon to explain his cosmological Doctrine of Ideas. (shrink)