A very nice example is given herein. Although fire is pure, still there is smoke. Yet smoke does not make the fire impure. Even though there is smoke in the fire, fire is still considered to be the purest of all elements. If one prefers to give up the work of a ksatriya and take up the occupation of a brahmana, he is not assured that in the occupation of a brahmana there are no unpleasant duties. One may then conclude that in the material world no one can be completely free from the contamination of material nature. This example of fire and smoke is very appropriate in this connection. When in wintertime one takes a stone from the fire, sometimes smoke disturbs the eyes and other parts of the body, but still one must make use of the fire despite disturbing conditions. Similarly, one should not give up his natural occupation because there are some disturbing elements. Rather, one should be determined to serve the Supreme Lord by his occupational duty in Krsna consciousness. That is the perfectional point. When a particular type of occupation is performed for the satisfaction of the Supreme Lord, all the defects in that particular occupation are purified. When the results of work are purified, when connected with devotional service, one becomes perfect in seeing the self within, and that is self-realization.