Answer

Tirthankars are Arihants, not Siddhas while they are living in the body. After their final liberation, they become Siddhas.

Explanation

In Jain Dharma:

• Arihant = a soul that has destroyed the inner enemies like anger, pride, deceit, greed, and has attained kevalgnan, but is still living in a body.
• Tirthankar = a special type of Arihant who establishes the Jain path and the fourfold Jain order.
• Siddha = a liberated soul that has completely left the body and all karma, and resides in Siddhashila.

So the sequence is:

• Before moksha: Tirthankar = Arihant
• After moksha: the same soul becomes Siddha

Spiritual Understanding

This distinction is very important in Jain Dharma because it shows the difference between:

• Realized soul in human form — Arihant / Tirthankar
• Fully liberated soul — Siddha

A Tirthankar is worshipped for showing the path. A Siddha is worshipped as the perfected state of freedom.

Takeaway

A Tirthankar is an Arihant during life, and a Siddha after liberation.