Freud elucidates 'thanatos' or the death drive in relation to the pleasure principle in his definition of the Nirvana principle:
Different from the pleasure principle in that pleasure sometimes increases with tension, and the Nirvana Principle is primarily under the sway of the death drive, whereas the pleasure principle is powered by Eros4.
4 Craig Chalquist, Nirvana Principle in A Glossary of Freudian Terms, available at http://www.terrapsych.com/freud.html.
In his formulation of the death drive Freud is validates two contradicting notions: the first describes death as the Nirvana principle (death is the discharge of all excitations), while the second regards the death drive as aggression, destructive energy generating violence and tension.
The close association between the pleasure principle and the Nirvana principle makes the life and death drives linked (the Nirvana principle serves and expresses the death drives).
He does so by offering a theoretical construct in the form of an aggressive drive but also posits the Nirvana principle as the aim of all organic systems to rid themselves of excitation and strive towards complete rest.
For example, Freud drew on Sanskrit ideas for his Nirvana principle
or death instinct.
He labeled this the principle of neuronal inertia, or the Nirvana principle
, and finally erected it into his concept of the death drive that dictated the inevitable fate of human life to be death.