Vaiśeṣika organized all objects of experience into what they called "padārtha"s (literally: 'the meaning of a word') which included six categories; "dravya" (substance), "guṇa" (quality), "karma" (activity), "sāmānya" (generality), "viśeṣa" (particularity) and "samavāya" (inherence). Later "Vaiśeṣika"s ("Śrīdhara" and Udayana and "Śivāditya") added one more category "abhava" (non-existence). The first three categories are defined as "artha" (which can be perceived) and they have real objective existence. The last three categories are defined as "budhyapekṣam" (product of intellectual discrimination) and they are logical categories.