Karl Marx is the author of The Communist Manifesto (with Friedrich Engels) and Capital. He was a highly influential philosopher, economist, historian, and sociologist whose theories formed the basis of most 20th century Communist societies. Dialectical Materialist. 
 

“A commodity is therefore a mysterious thing, simply because in it the social character of men's labour appears to them as an objective character stamped upon the product of that labor; because the relation of the producers to the sum total of their labour is presented to them as a social relation, existing not between themselves, but between the products of their labour. This is the reason why the products of their labour become commodities, social things whose qualities are at the same time perceptible and imperceptible by the senses. In the same way the light from an object is perceived by us not as the subjective excitation of our optic nerve, but as the objective form of something outside the eye itself. But, in the act of seeing, there is at all events, an actual passage of light from one thing to another, from the external object to the eye. There is a physical relarelation between physical things. But it is different with commodities. There, the existence of the things qua commodities, and the value relation between the products of labour which stamps them as commodities, have absolutely no connection with their physical properties and with the material arising therefrom. There is a definite social relation between men, that assumes, in their eyes, the fantastic form of a relation between things.”  

– Karl Marx, Capital