"What is milk like? Oh, you say, it is something white. You cannot think of the milk without the whiteness, and again, you cannot think of the whiteness without the milk.
"Thus one cannot think of Brahman without Śakti, or of Śakti without Brahman. One cannot think of the Absolute without the Relative, or of the Relative without the Absolute.
"The Primordial Power is ever at play. She is creating, preserving, and destroying in play, as it were. This Power is called Kāli. Kāli is verily Brahman, and Brahman is verily Kāli. It is one and the same Reality. When we think of It as inactive, that is to say, not engaged in the acts of creation, preservation, and destruction, then we call It Brahman. But when It engages in these activities, then we call It Kāli or Śakti. The Reality is one and the same; the difference is in name and form.
"It is like water, called in different languages by different names, such as 'jal', 'pani', and so forth. There are three or four ghats on a lake. The Hindus, who drink water at one place, call it 'jal'. The Mussalmans at another place call it 'pani'. And the English at a third place call it 'water'. All three denote one and the same thing, the difference being in the name only. In the same way, some address the Reality as 'Allah', some as 'God', some as 'Brahman', some as 'Kāli', and others by such names as 'Rama', 'Jesus', 'Durga', 'Hari.' "
Source: Sri Ramakrishna Jivan Charitra (Gospel of Sri Ramakrishna) by M