"O sinless one, the mode of goodness, being purer than the others, is illuminating, and it frees one from all sinful reactions. Those situated in that mode develop knowledge, but they become conditioned by the concept of happiness."
"The living entities conditioned by material nature are of various types. One is happy, another is very active, and another is helpless. All these types of psychological manifestations are causes of the entities' conditioned status in nature. How they are differently conditioned is explained in this section of Bhagavad-gita. The mode of goodness is first considered. The effect of developing the mode of goodness in the material world is that one becomes wiser than those otherwise conditioned. A man in the mode of goodness is not so much affected by material miseries, and he has a sense of advancement in material knowledge. The representative type is the brahmana, who is supposed to be situated in the mode of goodness. This sense of happiness is due to understanding that, in the mode of goodness, one is more or less free from sinful reactions. Actually, in the Vedic literature it is said that the mode of goodness means greater knowledge and a greater sense of happiness.
The difficulty here is that when a living entity is situated in the mode of goodness, he becomes conditioned to feel that he is advanced in knowledge and is better than others. In this way he becomes conditioned. The best examples are the scientist and philosopher: each is very proud of his knowledge, and because they generally improve their living conditions, they feel a sort of material happiness. This sense of advanced happiness in conditioned life makes them bound by the mode of goodness of material nature. As such, they are attracted toward working in the mode of goodness, and, as long as they have an attraction for working in that way, they have to take some type of body in the modes of nature. Thus there is no likelihood of liberation, or of being transferred to the spiritual world. Repeatedly one may become a philosopher, a scientist or a poet, and repeatedly become entangled in the same disadvantages of birth and death. But, due to the illusion of the material energy, one thinks that that sort of life is pleasant."
"The mode of passion is born of unlimited desires and longings, O son of Kunti, and because of this the embodied living entity is bound to material fruitive actions."
"The mode of passion is characterized by the attraction between man and woman. Woman has attraction for man, and man has attraction for woman. This is called the mode of passion. And, when the mode of passion is increased, one develops the hankering for material enjoyment. He wants to enjoy sense gratification. For sense gratification, a man in the mode of passion wants some honor in society, or in the nation, and he wants to have a happy family, with nice children, wife, and house. These are the products of the mode of passion. As long as one is hankering after these things, he has to work very hard. Therefore it is clearly stated here that he becomes associated with the fruits of his activities and thus becomes bound by such activities. In order to please his wife, children and society and to keep up his prestige, one has to work. Therefore, the whole material world is more or less in the mode of passion. Modern civilization is considered to be advanced in the standards of the mode of passion. Formerly, the advanced condition was considered to be in the mode of goodness. If there is no liberation for those in the mode of goodness, what to speak of those who are entangled in the mode of passion?"
"O son of Bharata, the mode of darkness causes the delusion of all living entities. The result of this mode is madness, indolence and sleep, which bind the conditioned soul."
"...The mode of ignorance is a very peculiar qualification of the embodied soul. This mode of ignorance is just the opposite of the mode of goodness. In the mode of goodness, by development of knowledge, one can understand what is what, but the mode of ignorance is just the opposite. Everyone under the spell of the mode of ignorance becomes mad, and a madman cannot understand what is what. Instead of making advancement, one becomes degraded. The definition of the mode of ignorance is stated in the Vedic literature. Vastu-yathatmya-jnanavarakam viparyaya-jnana-janakam tamah: under the spell of ignorance, one cannot understand a thing as it is. For example, everyone can see that his grandfather has died, and therefore he will also die; man is mortal. The children that he conceives will also die. So death is sure. Still, people are madly accumulating money and working very hard all day and night, not caring for the eternal spirit. This is madness. In their madness, they are very reluctant to make advancement in spiritual understanding. Such people are very lazy. When they are invited to associate for spiritual understanding, they are not much interested. They are not even active like the man who is controlled by the mode of passion. Thus another symptom of one embedded in the mode of ignorance is that he sleeps more than is required. Six hours of sleep is sufficient, but a man in the mode of ignorance sleeps at least ten or twelve hours a day. Such a man appears to be always dejected and is addicted to intoxicants and sleeping. These are the symptoms of a person conditioned by the mode of ignorance."
"The mode of goodness conditions one to happiness, passion conditions him to fruits of action, and ignorance to madness."
"A person in the mode of goodness is satisfied by his work or intellectual pursuit, just as a philosopher, scientist, or educator may be engaged in a particular field of knowledge and may be satisfied in that way. A man in the modes of passion and goodness may be engaged in fruitive activity, he owns as much as he can and spends for good causes. Sometimes he tries to open hospitals, give to charity institutions, etc. These are the signs of one in the mode of passion. And the mode of ignorance covers knowledge. In the mode of ignorance, whatever one does is neither good for him nor for anyone."
"Sometimes the mode of passion becomes prominent, defeating the mode of goodness, O son of Bharata. And sometimes the mode of goodness defeats passion, and at other times the mode of ignorance defeats goodness and passion. In this way there is always competition for supremacy."
"When the mode of passion is prominent, the modes of goodness and ignorance are defeated. When the mode of goodness is prominent, passion and ignorance are defeated. And when the mode of ignorance is prominent, passion and goodness are defeated. This competition is always going on. Therefore, one who is actually intent on advancing in Krsna consciousness has to transcend these three modes. The prominence of some certain mode of nature is manifested in one's dealings, in his activities, in eating, etc. All this will be explained in later chapters. But if one wants, he can develop, by practice, the mode of goodness and thus defeat the modes of ignorance and passion. One can similarly develop the mode of passion and defeat goodness and ignorance. Or, one can develop the mode of ignorance and defeat goodness and passion. Although there are these three modes of material nature, if one is determined, he can be blessed by the mode of goodness, and by transcending the mode of goodness he can be situated in pure goodness, which is called the vasudeva state, a state in which one can understand the science of God. By the manifestation of particular activities, it can be understood in what mode of nature one is situated.
Bhagavad-gita 14:6-10, Text and Purport
Bhaktivedanta Book Trust. HDG A.C. Bhaktivedanta Swami Srila Prabhupada.