That which is achieved through contemplation in Satya Yuga, through sacrifices in Treta Yuga, and through the worship of Lord Hari in Dvapara Yuga, may be attained through Kirtana or loud chanting of Lord Vishnu’s Name in Kali Yuga or Iron age.

In the Satya Yuga, the mind of men was generally pure. They had no distraction of the mind. There were neither cinemas, nor hotels, nor dancing halls and similar other distractions. Hence, meditation was easy and natural for them. That is the reason why contemplation has been prescribed for men of Satya Yuga. In the Treta Yuga, materials for the performance of Yajnas or sacrifices were easily available. The people had active tendencies. Therefore it was easy for them to perform Agnihotra, Jyotistoma, Darsa-Paurnimas and other Yajnas. That is the reason why Yajna has been described as the external form of Sanatana Dharma in that age. In the Dvapara Yuga, there was the manifestation of Avataras and men could easily have direct worship of God. Hence, worship was prescribed as the principal form of Sadhana in that age. In the Kali Yuga, there are many distractions for the mind. People lack in Brahmacharya, strength of will and power of enquiry or rational investigation. It is very difficult to procure materials for the performance of sacrifices. Therefore, Hari Kirtana or loud chanting of the Divine Name and selfless service of humanity have been recommended as the principal forms of Sadhana.