Emptiness (sunyata) is knowing that all things in their conventional or mundane aspect are non-substantial.
Signlessness (animittata) is the emptiness of signs. It refers to not seizing upon things in their mundane aspect and using them as objects for clinging.
Wishlessness (apranihitata) is abstaining from actions based on passion and desire.
Nagarjuna tells us that the three gates also correspond to knowledge, wisdom, insight, and that they are called samadhi because the gates cannot be entered without a “collected mind.” Without this crucial element the gates cease to be gates and become only “cases of confusion.” Using samadhi as an expedient, one enters the city of Nirvana free of passion and this is the real freedom, “the residueless of freedom.”
Dharma then is the path that leads to the three gates and samadhi or meditation is the vehicle that carries us along the path and into the city. Those who say that meditation does not lead to freedom or Nirvana do not understand that in teaching samadhi it was like the Buddha handing us the keys to the car.
The city is not a real city because Nirvana is not a place but a state of mind. The gates themselves are only expedients in terms of emptiness, signlessness, and wishlessness. In respect to knowledge, wisdom, and insight, these are the glimpses of enlightenment or Buddhahood we collect as we fare along the path. Yet, it should be obvious that none of these things are within our reach as long as we remain in states of confusion. A confused mind cannot think clearly let alone see clearly enough to be able to even make out gates or cities.
In the Vimalakirti Nirdesa Sutra (as translated by Robert Thurman) it reads
What is ‘Joy in the pleasures of the Dharma’? . . . it is the joy of unbreakable faith in the Buddha . . . It is the joy of the renunciation of the whole world, of not being fixed in objects, of considering the five aggregates to be like murderers . . . It is the joy of always guarding the spirit of enlightenment, of helping other beings . . . it is the joy of the exploration of the three doors of liberation . . . it is the joy of acquiring liberative techniques and the conscious cultivation of the aids to enlightenment . . .
True renunciation is done in the mind. It has little to do with what one wears as clothes, or whether one’s head is shaved or not, or one’s lack of possessions. On the other hand, it has everything to do with using the expedient of samadhi.