It is very simple to understand. Suppose this hand, my hand, but how long it is hand? So long it is attached to the service of the body. If this hand is cut off from this body, it may be called hand, but it has no meaning. Similarly, head also. The head is head so long it is attached to the body. If the head is cut off from the body, then what is the meaning of this head? It has no meaning.
Similarly, either you become brāhmaṇa or you become kṣatriya or you become vaiśya or śūdra, if you are not attached to the service of the supreme whole, then you are useless brāhmaṇa, useless kṣatriya, useless vaiśya. This is the purpose. Therefore Kṛṣṇa has begun that cātur-varṇyaṁ mayā sṛṣṭaṁ guṇa-karma-vibhāgaśaḥ (BG 4.13). Therefore one has to understand what is the meaning of these different types of activities. Karmaṇo hy api boddhavyaṁ boddhavyaṁ ca vikarmaṇaḥ. Vikarmaṇaḥ means if you cannot work which will satisfy Kṛṣṇa, that is vikarma. That is vikarma, forbidden. Because the real purpose of working is to satisfy Kṛṣṇa. He is the center. He is the center of all activities. Sva-karmaṇā tam abhyarcya saṁsiddhiṁ labhate parām (BG 18.46). Simply by satisfying the central point, Kṛṣṇa, then you get saṁsiddhi. It doesn't matter whether you are a śūdra or a brāhmaṇa or engineer or lawyer. The real point is how to satisfy Kṛṣṇa.
But that education is lacking. So our Kṛṣṇa consciousness movement is teaching how to serve Kṛṣṇa from any position. It doesn't matter. Whether you are a brāhmaṇa, kṣatriya, vaiśya, śūdra, lawyer, engineer, or film actor or anything, it doesn't matter, but whether you are trying to satisfy Kṛṣṇa. That is the point. If you have no such sense, "I have to satisfy Kṛṣṇa," then it is śrama eva hi kevalam.