Fundamental human needs must be understood as a system: that is, all fundamental human needs are interrelated and interactive. With the exception of the need for livelihood, that is, to stay alive, there is no hierarchy in the system. On the other hand, simultaneities, complementarities and trade-offs are characteristics of the process of satisfying needs. There is no one-to-one correspondence between needs and satisfiers. A satisfier can simultaneously contribute to the satisfaction of different needs or, conversely, a need may require different satisfiers to be satisfied.