The 12^th Chapter begins with a question from Arjuna.  Arjuna asks whether saguna dhyānam or nirguna dhyānam is superior.  Saguna dhyānam means meditation up on the Lord with various features.  Nirguna dhyānam means meditation up on the lord with no features.  This question is wrong because the idea of superior comes only when you can choose.  According to Krishna, there is no choice between saguna dhyānam or nirguna dhyānam as everyone has to go through both.  Everyone needs to do both.  What saguna dhyānam can give, nirguna dhyānam cannot give, so both are compulsory.  They cannot be simultaneously practiced.  Everyone should start with saguna dhyānam, purify the mind, go to nirguna dhyānam and get moksha.  Krishna says that saguna dhyānam is superior, but nirguna dhyana devotees will reach him.  The benefits of saguna dhyānam is not material wealth, but transformation of inner personality. 

Verses 3 and 4

Having restrained the sense organs, being even-minded towards all, and being interested in the welfare of all beings, some (devotees) meditate upon the imperishable (Brahman) which is indefinable, unmanifest, all-pervading, incomprehensible, immutable, immoveable, and eternal.  They attain Me alone.

There are people who follow nirguna dhyānam as part of jñāna yoga.  In these three verses, Krishna is elaborating jñāna yoga, which is nirguna dhyānam nidhithyasanam.  Nirguna eeswara is:   

• Avyaktam:  Not perceptible to any sense organs.  The universe is made up of five element and our five sense organs recognize each one of them.  When we close the five sense organs, and then meditate upon nirguna Brahman.  Brahman or nirguna brahman is inconceivable, imperceptible, incomprehensible and indescribable or in one word unobjectifiable or Aprameya.  Nirguna Brahman is everywhere.  Saguna Brahman is finite and can move from one place to another.  But nirguna Brahman is infinite and formless and all-pervading and cannot move from one place to another.  Nirguna Brahman is free from spatial limitation.
• kūṭastham:  Brahman is free from sixfold modifications caused by kala tattvam – time.  kūṭa is also the anvil, the base used by iron smith for hammering iron.  Up on the anvil, the smith places the hot metal and shapes the metal.  The metal undergoes change, but the anvil remains chanceless.  Nirguna brahman is like kūṭa or anvil that does not change.  Changeless substratum is required for all changes.  All lifestyle event shape our personality, but the witness principle, the Brahman remains changeless.

How can we meditate up on a featureless Brahman.  Krishna says one must qualify oneself for such mediation.

The preparation for nirguna eeswara dhyānam is fourfold qualifications are sädhana catuṣṭaya saṃpatti or:

• Discrimination
• Dispassion
• Discipline
• Desire

Sädhana catuṣṭaya Saṃpatti is described in these verses. 

Krishna has said that nirguna eeswara is not objectifiable, that eeswara can exist in only one way.  The un-experienceable principles is experiencer alone.  Therefore, nirguna dhyānam is mediating up on myself, the atma or meditating up on the meditator.  Therefore, the mediator must be non-extrovert at the time of nirguna dhyānam.

• Mastering indirya grama or group of five sense organ
• Maintaining equanimity under all circumstances.  The mind must be free from raga dwesha – likes and dislikes.
• Being committed to the well beings of all creatures; universal love; Expanded mind;  Mind must be sensitized to feel the difficulties of others and interested in their wellbeing.    

Verse 5

Difficulties are more for those people whose minds are committed to the pursuit of the unmanifest Brahman, for the goal of unmanifest Brahman is attained with difficulty by the people of bodily attachment. jñāna yoga is difficult because the destination of the formless one is difficult to reach; a highly refined mind is required.  jñāna yoga requires sravanam, mananam and nidhithyasanam and nidhithyasanam is jñāna yoga.  The difficulties of people committed to jñāna yoga is many.  Because the destination of the formless Brahman, is difficult to reach.  The common obstacle is deha abimana or strong attachment to one’s own physical body and we are busy maintaining and improving the body.  Stronger the body attachment, the more  difficult jñāna yoga.