consider whether knowledge is a thing you can possess that way without having it about 
you, like a man who has caught some wild birds -pigeons or whatnot- and keeps them in 
an aviary he has made for them at home. In a sense, of course, we might say he ‘has’ them 
all the time in as much as he possesses them, mightn’t we?...But in another sense he ‘has’ 
none of them, though he has got control of them, now that he has made them captive in an 
snclosure of his own; he can take and have hold of them whenever he likes by catching any 
bird he likes, and let them go again, and it is open to him to do that as often as he pleases. 
(Plato, Theaetetus, 197e, in Hamilton & Cairns, 1961, pp. 903-904) 
Plato's greatest contribution, however, to the psychology of property was that his theories 
served as a target for Aristotle’s criticisms. 
Aristotle 
Aristotle was the student of Plato and stands in the same philosophical traditions. 
However, possibly because his father was an lonian physician, Aristotle tempered his 
philosophy with biology and other natural sciences (Barker, 1952), As a consequence, 
Aristotle’s discussions of property in the Politics (Barker, 1952) are concerned more with 
psychological reality than with philosophical idealism. Aristotle used all five of the 
psychological explanations discussed earlier, particularly that property is self-centered, innate, 
and necessary for moral development: 
There is a further consideration which must be taken into account. This is the 
consideration of pleasure. Here too as well as in the matter of goodness, to think of a thing 
as your own makes an inexpressibie difference. The satisfaction of a natural feeling brings 
pleasure; and it may well be that regard for oneself and, by extension, for what Is one’s own, 
is a feeling implanted by nature, and not a mere random impulse. Self-love is rightly 
censured, but what is really censured is not so much love of oneself as love of oneself in 
excess -just as we also blame the lover of money not so much for loving money as for 
loving it in excess; the simple feeling of love for any of these things, self, or property, or 
money, is more or less universal. We may add that a very great pleasure is to be found in 
doing a kindness and giving some help to friends, or guests, or comrades; and such 
kindness and help become possible only when property is privately owned. (Aristotle, 
Politics, 1263b, in Barker, 1952, p. 50) 
Aristotle emphasized that the private property institution of the household provides the leisure 
and material resources needed for friendship, for acts of benevolence, and for participation in 
civic affairs, which are all necessary for moral development, and ultimately, for becoming a 
rational! man (Mathie, 1979). Aristotle argued that moral development, as distinct from moral 
behavior, cannot be legislated. Property must be owned before it can be shared or given away. 
Aristotle argued that private property results in more sharing and more social harmony than 
does communal property: 
When everyone has his own separate sphere of interest, there will not be the same ground 
for quarrels; and the amount of interest will increase, because each man will feel that he is 
applying himself to what is his own. And on such a scheme, too, moral goodness and not, 
as in Plato’s scheme, legal compulsion, will ensure that the property of each is made to