In our core case, the beneficial legal owner (A) of a certain asset transfers, or purportedly transfers, outright beneficial legal ownership in that asset to a transferee (B) in circumstances where the transaction between A and B must be considered as somehow defective. Any analysis of whether A might identify proprietary rights in that asset, or in a substitute thereof, must start with the question of whether legal ownership in the original asset has passed to B, at least in a first instance, or whether A has retained it ab initio. This issue has been thoroughly analysed by the author elsewhere, which is why reference may broadly be made to that publication.

There are basically three different modes of how legal ownership in tangible movable property may be consensually transferred (inter vivos) from one person to another, namely delivery, sale and deed. As far as the scope of those modes of transfer is concerned, the conclusion has been reached that delivery or a deed is only but always required if the transfer is gratuitous, i.e. for no consideration, or if the transferred chattel is corporeal money. It has furthermore been argued that each of those three modes of transfer is governed by a principle of separation, in the sense that real conveyance is notionally distinct and separate from an underlying obligatory transaction, for example a contract, and by a principle of abstraction, which means that the conveyance's effectiveness is not dependent on the existence or validity of such an underlying contract or other obligatory transaction. To convey legal title, it is – with regard to each of those three modes of transfer – basically required that the transferor sufficiently intends to transfer legal ownership and that the transferee (sooner or later) sufficiently intends to receive it. The combination of those two intentions has been called a real agreement.

If this real agreement – i.e. the transferor's intention to transfer property and/or the transferee's intention to receive it – is sufficiently affected (rendered void) by a certain defect, legal ownership does not pass to the transferee ab initio. This is evidently the case if the transferor has not intended to transfer ownership at all, as in cases of theft, loss or misappropriation, or if a corresponding intention of another person is not attributable to the legal owner (lack of authority).