Tibetan Buddhism is a Mahayana Buddhist tradition, meaning that the goal of all practice is to achieve enlightenment (or Buddhahood) in order to help all other sentient beings attain this state, as opposed to mere personal liberation. The motivation for Mahayana practice is Bodhicitta (a Sanskrit word meaning 'mind of enlightenment') --the altruistic intention to become enlightened for the sake of all sentient beings. Buddhahood is defined as a state of omniscience (sarvajñä) that is freedom from the obstructions to liberation (or negative states of mind such as ignorance, hatred and desirous attachment) and the obstructions to omniscience (which are the imprints or 'stains' of delusions imagining inherent existence). When one is freed from mental obscurations one is said to attain a state of continuous bliss mixed with a simultaneous cognition of the true nature of reality, where all limitations on one's ability to help all other living beings are removed. This includes the attainment of omniscience - that is the removal of all obstructions to knowing all phenomena (or seeing the empty nature of each phenomenon as well as each of their relative characteristics). From the perspective of Tibetan Buddhism, when one conceives of a particular object the mind gives rise to the appearance of that object. In perceiving the empty nature of all phenomena as well as each of their relative characteristics, one becomes both omniscient and omnipresent. There are said to be countless beings that have attained Buddhahood, or countless Buddhas. Buddhas spontaneously, naturally and continuously perform activities to benefit all sentient beings. However it is believed that sentient beings' karma (or 'actions') limit the ability of the Buddhas to help them. Thus, although Buddhas possess no limitation from their side on their ability to help others, sentient beings continue to experience suffering as a result of the limitations of their own former negative actions.