肇論新疏 1.21

1.21

以此而推，故知雖今現有，有而性常自空。性常自空，故謂之性空。

Inferring from this, we therefore know that although they are presently existing now, existing, their nature is ever of itself empty. Because their nature is ever of itself empty, they are called prakṛti-śūnyatā.