In Jain philosophy, the concepts of Dravya (substance), Guna (quality), and Paryaya (modification or mode) are central to understanding reality.

1. Vastu simply means an entity or reality. Every Vastu has three aspects: Dravya, Guna, and Paryaya.

- Dravya is the underlying substance. - Guna are the inherent qualities of the Dravya. - Paryaya is the modification or state in which the substance exists at a particular time.

1. Dravya as a part of Tattva:

- In Jain metaphysics, Tattva refers to the fundamental principles or realities, mainly explained as seven (sometimes nine). These include Jiva (soul), Ajiva (non-soul), Asrava (influx), Bandha (bondage), Samvara (stoppage), Nirjara (shedding), and Moksha (liberation). - The first two, Jiva and Ajiva, are themselves Dravyas (substances)—Jiva Dravya (soul substance) and Ajiva Dravyas (five types of non-soul substances). - So, Dravya (substance) is included within Tattva because understanding the nature of substance (Jiva and Ajiva) is essential to understanding the reality described by Tattva. - Guna and Paryaya, while important, are always dependent on Dravya. They cannot exist independently; they are the attributes and states of Dravya.

In summary:

• Vastu refers to any real entity, characterized by Dravya, Guna, and Paryaya.
• Out of these, Dravya is significant in Jain metaphysics and is counted among the Tattvas (as Jiva and Ajiva).
• This is because Dravya is the substratum that possesses qualities (Guna) and modes (Paryaya), and only Dravya can be directly linked to the path of liberation, which is the focus of the Tattva doctrine.

References:

• Tattvartha Sutra by Acharya Umasvati, especially the commentaries on the first and second chapters.
• Pravachanasara by Acharya Kundakunda.