In Jainism, Sarvagya / Sarvajña = Kevali = one who has Keval‑jnān (perfect omniscience). We cannot “prove” this like a lab experiment, but Jain ācāryas give strong logical reasons to accept that omniscience can and does exist.

I’ll keep it step‑by‑step and simple.

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1. Nature of soul: knowledge is its basic quality

Jain philosophy says:

• Every jīva (soul) has:

- Jnāna – knowing power - Darshan – perceiving power

• These are natural, infinite in the pure soul.
• Why do we know only a little now?

Because our karmas cover this natural, infinite knowledge (especially jñānāvaraṇīya karma).

So:

> If a veil is covering a lamp, light is dim. > Remove all veils, light becomes full and unlimited.

Similarly:

• When all knowledge‑covering karmas are fully destroyed,

the soul’s natural, infinite knowledge appears. That is called Keval‑jnān (Sarvajñatā, omniscience).

So, in Jain view:

• Omniscience is not “given” from outside.
• It is the natural state of every soul, when karmic coverings are gone.

You can read a simple definition of Keval‑jnān here:

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2. We actually see degrees of knowledge

Look at reality:

• Some people know more than others.
• Some have extraordinary memory, sharp insight, etc.
• Jain texts speak of higher levels:

- Mati‑jnān – normal sense‑knowledge - Śruta‑jnān – scriptural, learned knowledge - Avadhi‑jnān – clairvoyant (distant, subtle objects) - Manaḥparyāya‑jnān – knowing others’ thoughts - Keval‑jnān – perfect omniscience

Logic used by Jain ācāryas:

1. We already accept that knowledge can increase – from little to more, and to very high levels.
2. There is no logical limit where we can say, “knowledge must stop here; beyond this no further clarity is possible.”
3. If there is no fixed upper limit, then infinite, perfect knowledge is possible when all obstacles (karmas) end.

So Sarvajñatā is simply the highest point on the same scale of knowledge which we see every day in small form.

You can see an easy explanation of five types of jñān here:

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3. Scriptural and logical testimony

Jainism gives three main supports to accept Sarvagya:

1. Agam / Āpta‑vāṇī (Scripture & trustworthy teachers)

- Teachings of Tīrthankars are declared: - internally consistent, - covering all aspects of reality (soul, karma, bondage, liberation, matter, space, time, dharmāstikāy, adharmāstikāy, etc.), - unchanged and working in practice for centuries. - Such total, flawless knowledge cannot come from an ordinary, limited mind – it indicates an omniscient source.

1. Artha‑kriyā‑kāritva (Practical success)

- The path shown by them: - removes passions, - purifies conduct, - creates inner peace, detachment, and high virtues in followers. - A teaching that consistently leads to its promised goal (śuddhi, mokṣa) is taken as coming from a perfect knower (Sarvajña).

1. Absence of refutation (abādhita‑jñān)

- Jain epistemology says: Knowledge that is: - self‑consistent, - consistent with experience, and - never refuted by stronger knowledge is taken as true. - For millennia, no system has able to logically destroy the Jain structure of reality (anekānt, syādvāda, karma theory, types of jñān, etc.). This supports that its source is not ordinary, but Sarvajña.

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4. Objection: “If Sarvagya exists, why can’t I see him now?”

Jain answer:

• Time is beginningless, and in each half‑cycle of time there are 24 Tirthankaras, each becoming Sarvajña Kevali.
• In our present era, all 24 have already attained mokṣa, so no living Sarvajña is present now.
• But:

- Their teachings (Āgamas) remain. - The line of ācāryas and munis who preserved and practised this path are visible history. - The results of following the path (inner purity, non‑violence, restraint) can be observed even today.

Thus, we infer the past existence of Sarvajñas from:

• the nature of soul and karma,
• the gradation of knowledge,
• the depth and consistency of Jain doctrine,
• and the living impact of its practice.

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5. Digambar & Śvetāmbara: any difference here?

On existence and nature of Sarvajña / Kevali, both traditions agree:

• Kevali has:

- Anant‑jnān (infinite knowledge) - Anant‑darshan - Anant‑vīrya - Anant‑sukha

• Keval‑jnān arises only after total destruction of the four ghāti‑karmas.
• Such a Kevali is truly Sarvagya – knowing all substances and all modes of all times.

Differences between Digambar and Śvetāmbara are not about whether Sarvajña exists, but about:

• some historical details,
• text preservation,
• and conduct rules of monks.

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6. Summary in very simple words

1. Soul’s nature = to know. In pure state, its knowing is infinite.
2. Karma covers this infinite knowledge, so now we know only a little.
3. If all covering karmas are completely removed, soul’s infinite knowledge shines fully.
4. That state is Keval‑jnān / Sarvajñatā – the soul becomes Sarvagya.
5. The depth, completeness and effectiveness of Jain teachings, plus the gradual scale of knowledge we see, support that such Sarvagya Kevalis have really existed (Tirthankaras).

So, from the Jain philosophical standpoint, the existence of Sarvagya is not blind belief, but a logical conclusion based on:

• the nature of soul,
• observable degrees of knowledge,
• and the unique, flawless character of Tirthankars’ teachings.