Pleasure-pain principle

One often sees this term in its shortened form pleasure principle. The reference here is to a hypothetical early and primitive id function that seeks to satisfy any need either by direct means or through hallucination and fantasy -- with the implication that at this point in an infant's development there is a failure to differentiate the fantasy from the reality. According to the standard Freudian model, the primitive, pleasure-seeking, pain-avoiding operations gradually become modified by the reality principle as ego functions are developed and the child comes to replace the fantasized wish fulfillment with more appropriate and reality-oriented adaptive behavior. Note also that the pain of the principle is different in meaning from the pain in the pain principle, where a striving for pain is hypothesized, not an avoidance of it.