Antigone: Nor did I think your orders were so: strong that you, mortal man, could over-run gods' unwritten and unfailing laws. Not now, nor yesterday's, they always live, and no one knows their origin in time (Sophocles, Antigone, lines 453-57). Karl Marx was convinced that private ownership of capital goods was social and moral evil. There thesis that this conviction of Marx rests predominantly upon natural law. This paper accepts that thesis. The discussion in this paper meant to substantiate natural law foundation of Marx's property position. There will be no elaborate attempt, however, to prove thesis. The purpose of this paper to discuss why Marx postulated that private property an evil institution which had to be eradicated from society. Before judging Marx's conclusion helpful to know various logical steps by which that conclusion derived. It important to realize that arguments put forth here are meant to be, primarily if not exclusively, logical and neither psychological nor psychoanalytical. In other words, what being sought logical unfolding of Marx's thought, not psychological factors influencing it. This paper contains three parts and final comments. First, there an exposition of concept of natural law. This done since natural law theory enters only limited areas of contemporary economic analysis and may not be familiar to many readers. Secondly, there discussion of thesis that Karl Marx's views on private property are based on natural law. Thirdly, reasons Marx rejected private property are put forth. The fact that this third pan in nature of reflection makes somewhat difficult to substantiate. I. The Concept of Natural Law(1) Natural law came originally from Greek philosophers, was furthered by Roman jurists, and received more ordered presentation from scholastic philosophers of twelfth through seventeenth centuries. The writings of St. Thomas Aquinas will be used here as basis for natural law explanation. The thought of St. Thomas does not represent culmination of thinking on this subject, but does provide wholly adequate background to topic. There are two general meanings of law.(2) When we speak of law of diminishing marginal productivity or law of gravity, term law means that specific outcome will take place granted certain conditions. Diminishing marginal productivity occurs at some point for each and every type of firm. It law because always takes place; at some level of input marginal product diminishes. Obviously this not type of law meant when speaking of natural law. The other general meaning of law which pertinent here that law rule or norm which prescribes some specific action or avoidance of action. Of this latter type of law one definition states: That which must be obeyed and followed by citizens, subject to sanctions or legal consequences, 'law' (Black's Law Dictionary, 1968, Law). While this definition of law refers to positive, human law, St. Thomas similarly defined law as a rule and measure of acts, whereby man induced to act or restrained from acting (I-II, q. 90, art. 1).(3) Again, he stated that law is nothing else than an ordinance of for common good, made by him who has care of community, and (I-II, q. 90, art. 4). St. Thomas organized law under four different categories: eternal law, natural law, divine law, and human (positive) law. We are concerned here primarily with first two of these four categories. Eternal law was defined by St. Thomas as the eternal decrees of God concerning government of universe (I-II, q. 91, art. 1). Eternal law supposes that there God who rules world by intelligence. The plan which God has for world called law: . . an ordinance of reason for common good; promulgated by its being imbedded in natures of creatures governed by it (Fagothey/Gonsalves, 1981, p. …