The concept of astikāya, found in Bhagavatī is very important. Acharya Mahaprajna has analysed it deeply. He writes in the commentary of Bhagavatī that- The doctrine of jiva tattva (soul) is accepted in many philosophies. Whether it is thumb-sized, body pervasive or all pervasive is well discussed subject but the discussions on its intrinsic nature such as how many atoms or pradeśas it is possessed of etc. are available nowhere else besides Jainism. By stating astikāya as aggregate of pradeśa, Lord Mahavira has expressed it in a novel dimension.
In Jain philosophy, existence means atom or an aggregate of atoms. Dharmāstikāya, adharmāstikāya, ākāśāstikāya and jīvāstikāya are atomic aggregates. Their atoms can never be separated, that's why these are called pradeśa. The atoms of pudgalāstikāya can be integrated and separated. So, these are found in both the states- atom and aggregate.
Only aggregates of jīvāstikāya are conscious out of five astikāyas. Pradeśa and skandha of the rest three astikāyas and pradeśa skandha and atoms of pudgalāstikāya (matter) are non-conscious i.e. ajīva.
Four astikāya out of five, are incorporeal and thus non-perceptible through senses). Pudgalāstikāya is corporeal and hence, is visible. Characteristics of incorporeal are absence of colour, smell, taste and touch. On the contrary the characteristics of corporeal is - presence of colour, smell, taste and touch.[1]
With the addition of time substance to the above said five astikāyas, the concept of six dravyas (substances) is postulated.[2]