Practice and detachment develop four types of samadhi: self-analysis, synthesis, bliss and the experience of pure being.
The deep absorption of attention on an object is of four kinds, 1) gross (vitarka), 2) subtle (vichara), 3) bliss accompanied (ananda), and 4) with I-ness (asmita), and is called samprajnata samadhi.
Deep concentration on an object consists of 4 types: 1. Gross thought (vitarka) 2. Subtle thought (vichara) 3. Bliss (ananda) 4. I-am-ness (asmita) and is called samprajnatah samadhi (unity with object and Divine)
This sutra is actually about the final stage of the eight limbs of ashtanga yoga – samadhi, or the seer becoming one with what is seen (Iyengar describes this as ‘awareness’).
Incidentally, I think that in a book, my mind would prefer to work up to samadhi, beginning with the more achievable limbs of yoga, rather than jumping straight in with the ultimate goal. I wonder why Patanjali did it this way? I suppose if you start with the ‘prize’ / goal, then the purpose of the lower stages is more obvious. Perhaps by doing this, he is saying that this whole book is about samadhi or meditation / awareness, and that the other 7 limbs are steps you must follow to achieve this.
This translation / interpretation of the yoga sutras says it helps to think of this sutra (on the nature of samadhi) as being about attention or concentration, or meditation. This particular sutra is on samprajnata samadhi – unity, cognitive non-duality or lower samadhi (compared with the next sutra, which is on asamprajnata samadhi, meditation without content).
The sutra states that there are four types of meditation or attention:
1. Iyengar calls the first type ‘self-analysis’, but the other translations refer to it as ‘gross thought’ or ‘gross concentration’. This means meditation upon physical objects, mantras, breath, etc.
2. Subtle thought – after the gross thoughts have been left behind, the subtle nature of things
3. Bliss – freedom from the gross and subtle thoughts,
4. I-am-ness or the experience of pure being – consciousness of being with oneself.
It appears that these are just listed as the four types of ‘meditation with content’, not that they are supposed to be done in a particular order or that one is superior to any other. I notice that this appears to be in quite stark contrast to Zen Buddhism, but perhaps not to other forms of Buddhism. In the Zen practice of zazen, or shikantanza (sitting meditation), one jumps straight in with formless meditation – just sitting, and noticing what occurs, with no particular focus on the breath or anything else. I suppose that the 4 types of meditation here would still occur if one only practiced zazen. By just sitting, you would still gain the awaresness of the gross and the subtle, of the bliss (if it happened to occur), and the I-am-ness.
I suspect that Zen Buddhists would take issue with the ‘bliss’ aspect here – Suzuki in ‘Zen Mind, Beginners Mind’ implies that you may or may not find meditation enjoyable / blissful / peaceful. If you did, then great, but that is not the point. The point is that you noticed it.