Between January and February of 1970, the American philosopher Saul Kripke delivered three significant lectures at Princeton University which were published as Naming and Necessity. In those lectures, in addition to criticising the descriptive theories, topics of major importance such as names, reference, rigidity, modality and necessity were raised. Based on his three lectures and the paper Identity and Necessity, which was published a year after the publication of Naming and Necessity (1971), the following four ideas will be developed: firstly, necessity and identity in the direct reference theories; secondly, rigid designators and possible worlds; thirdly, initial baptism; and finally, naming and necessity.