The article discusses economic theories in capitalist societies, comparing Keynes and Marx, exploring development theories, analyzing Marxian economics, and addressing environmental issues. It looks at the effects of technology on productivity, the role of GNP, and the mixed economy's impact on economic development. The researchers also examine Marx's theories on value, underconsumption, and capitalism's contradictions. Additionally, they discuss environmental pollution control, energy policies, and North-South relations on the environment. The article concludes with essays on disarmament, institutional economics, and a dialogue between Diderot and Marx on national income.