What does 'energy' mean?

A new student in my classes is bringing a 'beginner's mind' and asking fundamental questions, which are never a waste of time. In spiritual circles, no word get bandied about more than 'energy' -- and upon doing some of the assigned class reading, he asked, simply, "What does energy actually mean?" He wrote to me with these examples from our reading:
"Here are some of the ways Sally Kempton uses the word (in the Foreword to the Shakti Coloring Book), each of which seems different:

1) 'The deities here represent subtle archetypal energies that exist in the universe and within each of us.' and '[One can] work with the images and sacred sounds as focal points for meditation and, finally, attempt to bring the energy of the deity inside.'
2) 'I began to notice that the yantra evoked certain energies in me.' and 'But at the same time, it emanated a feeling of softness, a palpably sweet energy.'
3) 'Coloring these mandalas and deity drawings can be a profound spiritual practice, which can integrate the separated energies in your psyche and also connect you to their higher octaves.'

Does 'energy' mean different things in these contexts?"

My reply follows: 'Energy' usually translates the Sanskrit word shakti, which also means 'potency, power, capacity.' Literally the word 'energy' means 'the power to do (inner) work' -- both in English (from Gk. energeia) and in Sanskrit. Sometimes the word is used in a sloppy way in spiritual circles, obscuring this fundamental meaning. For example, it is used (improperly, in my view) as equivalent to Sanskrit bhāva, which means 'feeling', 'mental state', or even 'vibe' in English slang. (Such as "this place has a nice energy" which means "I feel good in this place" or "I like your vibe".) In Sally's usage above, #1 uses the word correctly to mean 'spiritual power that can effect inner transformation', while #2 uses it to simply mean feeling or bhāva.  #3 uses it as loosely equivalent to 'deities', aspects of one's being which need to be evoked and integrated in order to effect the inner transformation they are capable of. Certainly there are latent energies in your being that are activated through these practices.

This student wrote back:  "I do not fully understand this. Specifically:

1) What is an 'aspect of my being' here? Is it something like, say, being embodied, or having emotions, or sexuality - simply a part of experience or existence? Or something more?
2) What does it mean to 'integrate' it?
3) What is inner transformation?

If you could illustrate these, perhaps with some examples, I think I would understand much better and more clearly what is meant. (I've heard these words and phrases many, many times, but always without examples or explanations, and I've never understood them properly.)"

Wonderful! I thought. Too few students ask to clarify the fundamentals, and too few teachers address what is already assumed but never adequately understood. My response follows:

There are countless aspects to your being whether we're talking about your thoughtfulness, your sexuality (which itself subdivides into many aspects like animalistic, infantile, refined, or spiritual sexual expression), your playfulness, your capacity for self-sabotage, your capacity to honor & revere what flows through you, your capacity to experience radical freedom—and infinitely more. You are vast — you contain multitudes! And some of these aspects are already active and expressed to some degree, while others are latent and unexpressed. Some aspects cohere into a subtle pattern we call a deity. For example, Shiva relates your capacity to experience freedom & spaciousness with your capacity to be still & silent an important coherence that your mind wouldn't necessarily have identified. Pārvatī relates power & discipline with humility & softness, cohering them into a pattern which, when accessed, produces greater benefit to all beings than accessing any of those qualities individually. This one of the primary purposes of the deities: to show us patterns otherwise obscured, empowering patterns we can cultivate.

What we mean by integration is a huge topic, but briefly, there are many aspects of a person's being that do not operate in perfect harmony with the whole because those aspects have been rejected, judged, or demonized (sexuality is a good example, but there are many others, like one's capacity to act naturally & spontaneously, and other positive qualities like enthusiasm, that have been judged and repressed in some people). Any aspect of you that has been rejected (even mildly) becomes partially 'separated' or split off from the governing self-image, and can only be accessed in special circumstances. (In extreme examples of this, a person develops Dissociative Identity Disorder or 'split personalities' -- but we all have a moderate version of this until our yoga is complete.) So these separated/rejected aspects need to be reintegrated.

Other aspects of you are simply latent, lying dormant, yet to be expressed. But when previously latent aspects arise, they don't usually fit with the governing self-image, so they too need to be 'integrated' — which means fully accepted, allowed in, allowed to be part of you (which often necessitates softening or releasing existing static self-images). When this integration occurs with aspects that have been previously rejected, there is often a flood of emotion and/or prāna (life-force energy) that surges through one's being (especially if such integration is sudden rather than gradual), because each such aspect contains pent-up energy not accessible to the whole system as long as it is dis-integrated, energy which then becomes accessible and merges with the whole when it is integrated.

Though this might seem like psychology more than yoga, I am articulating principles found in yogic and tantrik texts (such as chapter 11 of The Recognition Sutras) but rarely elaborated in detail there, partially because they didn't have the systematic vocabulary we now have.

'Inner transformation', then, is this mysterious process of discovering and reintegrating these 'lost' parts of ourselves, as well as tapping into the full vastness of our authentic being through spiritual practice, both of which result in becoming a blissful mass of harmoniously unified awareness (Skt. chidānanda-ghana-svātma enabling us to allow unimpeded spontaneous expression of life-energy to flow through us for the benefit of all beings. (Despite the seemingly grandiose language, this can look and feel very simple & sweet.)

Addendum 1: We would be remiss in not adding a comment on that even more misused word commonly heard in spiritual circles, 'energetic'. Many people these days use 'energetic' to mean 'subtle' (Skt. sūkṣma), that is, 'not perceptible to the five senses'.  (I have even heard it used in yogāsana classes to mean 'isometric', presumably because isometric use of the muscles is not perceptible to external viewers.) This is just a misuse. Imagine translating sūkṣma-śakti as 'energetic energy'!  Please no. :)  

Addendum 2: as Ekabhūmi said, we should avoid forming fixed categories based on these teachings on shakti. Forming 'defined, controlled, structured, predictable categories' is problematic because these mental structures (vikalpas) quickly ossify and become petrified, thereby resisting the free flow of the processes we are alluding to here. Words, in this dimension of human experience, can only be pointers, not descriptors.