These are the five cosmic functions. Together they are called the five-fold activity (pancha-kRtyaM) of the Lord. This concept of pancha-kRtyaM is also mentioned by the Shaiva schools. The very word pancha-kRtyaM means and involves activity. And as we know, no activity is possible without the kArya-brahman (para-brahma-shakti) coming in. So we can take it that the original source is parA-shakti. She does it through the five agents of Hers, namely the five forms of divinity mentioned above. The shAnta (calm) ShivaM in its nascent state cannot act. When action takes place it takes place through parA-shakti in the form of the five-fold functions. ShivaM by itself does not produce the action. But it is in ShivaM, the paraBrahman, that the first vibration for action sprouts, by its own Shakti. But even before the action there must have been a will. This will is called the icchA-Shakti.