When Shakthi manifests as bliss, Shiva manifests as ananda (the total happiness, a stage that is beyond bliss). Both bliss and ananda are the products of consciousness. Therefore the subtle difference between them is only in the level of consciousness. Shiva is super conscious and Shakthi is sub conscious. What is the difference between these two levels of consciousness? Sub-conscious stage has impressions in the mind and super conscious stage is absolutely pure and without any impressions or vasanas. Super conscious stage is beyond consciousness and this stage is nothing but the ‘sunya’ as called by Buddhists. But the sub-conscious stage of Shakthi does not undermine her importance. On the other hand, it underlines Her importance. This is because vasanas or impressions of our mind are the cause for all our actions.
The level of consciousness of Shiva and Shakthi depends upon their acts. Shakthi has too many acts to perform whereas Shiva has no act to perform. He has already performed His only act of creating Shakthi. Since Shiva has no acts to perform, his level of consciousness or awareness is considered supreme, as he has no thoughts. Thought is necessary, only if you want to do an act. It could be other way round also, as acts also create thoughts. The thought at this stage is called desire. This description of Shiva perfectly fits the description of nirguna Brahman. We talk about consciousness or awareness as we have to be aware of something that is not visible. When a thing is not visible, then it has to be realized. It is like the breeze. You feel the tender breeze that is not visible to you. In the same way nirguna Brahman is not visible and has therefore to be realized. When we involve ourselves with too many thoughts and acts, we cannot reach the level of super conscious stage, as we continue to be deluded by too many impressions.
At the most, we can reach the level of sub-conscious stage. Sub-conscious stage is a stage where something extraneous to your mind forcing you to do certain act or acts. You are not even aware of your sub-conscious mind unless some thought triggers it. Typical example is Hanuman, who is not aware of his strength unless someone reminds him of his strength. Shakthi is the kinetic energy and controls everything sun, moon, planets, stars, living beings, literally everything. Without Shakthi no activity can take place in the universe. To put it in a different perspective, she is the mind and matter. Here She perfectly fits the description of saguna Brahman. She is sat (being), cit (sub consciousness) and ananda (the stage of bliss). There is difference between sat-cit- ananda stage of Shakthi and Shiva. Shiva’s sat-cit-ananda stage is complete and total in all respects. He is that (being), His cit is super consciousness and his ananda is total, not merely bliss. Shiva is beyond consciousness which is called pure consciousness. For creation, sustenance and dissolution, pure consciousness alone is not enough. This in combination with mind and matter alone can create, sustain and dissolve. This is the concept of Shiva-Shakthi union.
The union of nirguna Brahman and saguna Brahman is called the Brahman. Therefore, Shiva-Shakthi union alone is called the Brahman, not Shiva alone or shakthi alone. Apart from super-consciousness and sub-consciousness stages, there is yet another stage called un-consciousness. The un-conscious stage of the mind is its original form. It is not aware of anything unless the mind is afflicted by impressions caused by sensory organs. So the un-conscious stage of the mind is its purest form. This purest form of the mind first gets transformed into conscious mind and the experience of the conscious mind causes impressions called vasanas in the sub-conscious mind. This is how the karmas are accrued and gets embedded in the soul which undergoes rebirths.