In the Lotus Sutra the Buddha affirms that he employed nirvana (in its meaning of extinction, cessation, emptiness in a negative sense) as a didactic method to save people blinded by ignorance and dominated by the thirst for existence:

For this reason …
I set up a tactful way for them,
Proclaiming the Way to end sufferings,
Revealing it through nirvana.
Though I proclaim nirvana,
Yet it is not real extinction.
All existence, from the beginning,
Is ever of the nirvana nature.”

It is important for Westerners, who have had a distorted and negative view of the Buddhist concepts of void and nirvana, to reflect on these words. Void, in fact, being emptied itself, becomes fullness. This changing and impermanent world in which we live is itself the real world. Any difference between nirvana and samsara vanishes; and the same nirvana, which as a “designation” is also empty and unreal, becomes alive and concrete in the realization of life’s indivisibility, in the collapse of self-centeredness and in the awareness of the interrelatedness of all things.

Bodhisattvas, then, do not live as ascetics in the desert of their spiritual pride, insensitive to the sufferings of unenlightened beings. The plight of those who suffer misery and delusion stirs their hearts and spurs them to compassionate acts, to which they subordinate their quest for their own enlightenment, having already chosen lives of absolute nondualism. Far from enjoying a separate happiness, bodhisattvas feel a “vicarious suffering,” with others and in the place of others. They do not therefore “renounce” nirvana but emancipate themselves from the pursuit of a false aim, living the true nirvana in a “return” to the everyday world.
A Buddhist Kaleidoscope; Riccardo Venturini, A Buddha Teaches Only Bodhisattvas, Page 333-334