What does the Bhagavad Gita mean when it says caste is based on Gunas? Does it mean trained, external behavior, or genetic predisposition?
According to the various Smritis, Vedas, and ancient Vedic scholars and commentators, the word Guna in the Gita verse means genetic predisposition.
For reference, Gita verse 18.41 says:
The duties of the Brāhmaṇas, ...
It says that all four classes of men--brāhmaṇas, kṣatriyas, vaiśyas and śūdras--are distinguished by their quality of work. This is oopposite to the artificial caste system where people are judged by their birth.
brāhmaṇa-kṣatriya-viśāṁ śūdrāṇāṁ ca parantapa karmāṇi
pravibhaktāni svabhāva-prabhavair guṇaiḥ
Brāhmaṇas, kṣatriyas, ...
Does the Bhagavad Gita declare that caste is based on birth?
Yes it does, according to all ancient and orthodox Vedic commentators.
First, from chapter 1:
1.41 - When unrighteousness prevails, O Krishna the women of the clan become corrupt; when
women become corrupt, there arises intermixture of castes.
adharmābhi-bhavāt kṛṣṇa praduṣyanti kula-...
Jnyana Yoga alone has a chance of puffing up the ego and hence it is said that only Jnyana is not enough. Jnyana if done perfectly is enough to make you free. Bhakthi can eliminate the I even without the bhaktha being aware about it. Karma Yoga when practiced at the level of Akarma (giving up doership) can free a man to quite an extent. Well, Adi ...
Bhakti, Gyan, Karma and Dhyana Yog all lead to Gyan or wisdom of Self/God realization. Actually all the worldly things like body, ego, family etc., are Mithya or temporary but a normal bound soul similar to animals cant grasp it easily owing to past births intrinsic animal instincts. Thats why intellect is given to human in first place, that is used to ...
Upanishad does not say that Bhakti Yoga is not valid.
Mental activities relating to the Saguna Brahman  - such as are described in the Shandilya Vidya  are Upasanas
 Mental Activities - As distinguished from real knowledge. The Upasana is distinct from Jnana or knowledge as in the later case all differences between the ...
Sri Krishna was one of the greatest Yogi. It is not that easy to comprehend or correlate various issues.
Sri Krishna said:
ध्यायतो विषयान्पुंसः सङ्गस्तेषूपजायते।
सङ्गात् संजायते कामः कामात्क्रोधोऽभिजायते।।2.62।।
In the case of a person who dwells on objects, there arises attachment
for them. From attachment grows hankering, from hankering ...
Arjuna asks the same question to Krishna in the beginning of Chapter 3 of the Bhagavad Gita, called Karma Yoga:
If, O Krishna you consider that Buddhi (mind-development) [jnana yoga] is superior to Karma (action), why
do you urge me to engage in this terrible deed?
You confuse me with statements that seem to contradict each other; ...
Think of this; We all have that knowledge/Gyana that there is something called Mukti which is final destination. But all will attain mukti ? No. Because all are not doing the karma(like bhakti, dhyana etc.) prescribed in scriptures to attain it. Let's see what Krishna said in Bhagwat Geeta to support the statement.
In BG Chapter 3 verse 3; Lord Krishna says:...