Voluntary Termination of Business Agreement by Partner- Do I have to return his Initial investment?

Due to lack of participation, I have asked a partner to voluntarily terminate his interest in our business so I can move forward without hindrance. He says he will, but he wants his initial investment back. Our voluntary termination clause reads as follows: I have a very informal business agreement between myself and a partner. The business has not even moved to the manufacturing stage. He has not been returning emails, and I have asked him to voluntarily terminate his interest in the business. He says he will, but wants his investment back. Our voluntary termination clause reads as follows:5. Voluntary Termination. If one Partner wishes to terminate the business relationship, it is agreed that the terminating Partner relinquishes any and all rights to the future business if the remaining Partner continues. The business is in the early stages- no assets or sales. I say future profits are being relinquished and he has to right to demand money from future business. He disagrees.