There is, though, another form of kinyan by which the one that is acquiring the item performs the “action” aspect of the kinyan, e.g. he lifts it up but does not have the necessary da’as to acquire the item. The item’s giver will supply the da’as aspect of the kinyan. Reb Chaim suggests that in this form of kinyan, where the one acquiring the item performs the action aspect of the kinyan and only lacks the da’as aspect, we do not need to utilize the halacha of shelichus to import the da’as.
Therefore Tosfos can be of the opinion that in order to acquire something on behalf of someone else, one must utilize the halacha of shelichus – yet in order to perform da’as acheres makneh oso, one need not use the halacha of shelichus. So in Tosfos’s opinion, a minor can own an item if he acquired it by means of da’as acheres makneh oso.
