the natural state of a lamp is free of dust, so why is the soul automatically with karma? shouldn't it be in the reverse with free soul becoming trapped?

In Jain Dharma, the jīva (soul) is pure by nature, but it is not said to begin first as free and then later become trapped in a historical sense. Rather, karma bondage is beginningless in worldly existence.

So the correct Jain view is:

• The soul’s true nature is pure, conscious, blissful, and omniscient in potential.
• But in saṁsāra the soul has always been associated with karmic matter without any beginning.
• Because of mithyātva, kaṣāya, yoga — wrong belief, passions, and activity — new karma keeps binding.
• Liberation happens when all karma is shed.

About your lamp example

A lamp that has dust on it is still a lamp; its nature is to give light. Similarly, the soul’s real nature is purity, but due to karma its qualities are covered.

So Jainism does not say:

• “First there was a completely free soul, then karma trapped it.”

Rather it says:

• “The soul in worldly existence has been bound by karma since beginningless time.”

Why does this not mean the soul is originally dirty?

Because karma is external to the soul. It is not the soul’s own nature. It is like a covering.

This is why Jain texts speak of the soul as:

• by nature pure
• but by condition bound

Then what is the “reverse” idea?

The reverse is actually the Jain goal:

• bound soul → purified soul → liberated soul

That means the soul becomes free from karma through:

• right faith
• right knowledge
• right conduct
• tapas
• self-restraint
• ahimsa

In one line

The soul is not naturally karmic; it is naturally pure. But in worldly existence, bondage is beginningless, and liberation is the removal of that beginningless bondage.

If you want, I can also explain this using the Jain doctrine of anādi bandha and the difference between soul’s intrinsic nature and worldly condition.