No satisfactory definition of Dominium in Roman Law has yet been achieved. Amongst English writers Austin many years ago found great difficulty in this question while in modern times Professor Buckland has written ‘it is thus difficult to define Dominium precisely.’ Again, Poste, dealing with Gaius' discussion of dominium, says that his opening statements are ‘deplorably confused.’ These examples are enough to indicate the condition, of uncertainty which prevails. In my submission this uncertainty exists mainly because the conception of ususfructus has never yet been explained adequately. Of Possessio it has been said ‘the definition of Possessio to give the results outlined is a matter of great difficulty. No perfectly correct solution may be possible,’ and this statement is generally accepted as a correct assessment of the present position in juristic literature. But here, too, in my opinion, the reason is again connected with usufruct, for the possessio of the usufructuary has not yet been adequately determined. Gaius (2.93) tells us ‘usufructuarius vero usucapere non potest; primuum quod non possidet, sed habet ius utendi et fruendi.’ Ulpian holds that he had possessio in fact (‘Naturaliter videtur possidere is qui usum fructum habet’ D.41.2.12). On this subject Roby says ‘the fructuary was not strictly a possessor and therefore if he was deprived from enjoying he had not a claim to the original interdict de vi but in virtue of his quasi-possessio a special interdict was granted him.’ Austin saw difficulty in the whole problem of possessio. He wrote ‘by Savigny in his treatise on possessio it is remarked that the possessio of a right of usufruct … resembles the possessio of a thing, by the proprietor, or by an adverse possessor exercising rights of property over the thing. And that a disturbance of the one possession resembles the disturbance of the other. Now this must happen for the reason I have already stated:—namely, that the right of usufruct or user, like that of property, is indefinite in point of user. For what is possession (meaning legal possession not mere physical handling of the subject) but the exercise of a right ?’