The penis is perceived as a pleasurable part of the self and as a highly cathected external object. The penis meets the test of an external object: it can be perceived by special senses, for it can be seen and it can be touched by the hand. As an external object, it is subject to loss.

The penis acquires part of this importance in each phase of development. The differentiation of the self and the object world within the anaclitic mother-child relationship is accompanied by recurrent experiences of separation, loss, and anxiety. The establishment of the special sense modalities as a system of discrimination between object and self takes place during this time. During the anal phase, the child experiences loss of stool, a part of the self yet external to the self. Castration anxiety follows these models.