If you read the stories of saints and sages, you will find that their values, approach to problems, deductions, conclusions, ideas and predictions were entirely different. Why, because they were mad? No, because their minds had crossed over the border of the senses, and when you go beyond that barrier, it is called expansion of mind.
With expansion of mind comes liberation of energy. When your mind is expanding by practices or by itself, then a certain type of energy is released. In yoga and tantra that energy is called kundalini shakti. Shakti and kundalini are the two terms used to denote this force, which has to be liberated as you liberate butter from milk. Here I am using the word ‘liberation’, but not in the religious sense. You know how butter is released from milk by a certain process; in the same way, the force or energy can be liberated from matter, because matter contains energy, or matter is a state of energy, and by a certain process you can extract that force. Beyond the body are the senses. Beyond the senses is the mind. Beyond the mind is the intellect. Beyond the intellect is the psyche. Beyond the psyche is the self, and beyond the self is the universe or the cosmos. This is how you have to extract the force from within this body and this person, and that shakti is known as kundalini.
Something about this force is known by most yoga teachers and practitioners, because nowadays people are talking about it and many books have been written concerning it. Kundalini is not a myth or a metaphorical poem. It is a force lying dormant beneath our animal instinct. This force is supposed to be the evolutionary energy in humans.
Swami Satyananda Saraswati, In: “Introduction to Kriya Yoga”