It is said in Bhagavad-gītā that after many, many lives of philosophical research the wise man ultimately comes to the point of knowing that Vāsudeva, the Supreme Personality of Godhead, is everything, and therefore he surrenders unto Him. Such serious students in philosophical research are rare because they are very great souls. If by philosophical research one cannot come to the point of understanding the Supreme Person, then his task is not finished. His search in knowledge is still to be continued until he comes to the point of understanding the Supreme Lord in devotional service.
The opportunity for direct touch with the Personality of Godhead is given in Bhagavad-gītā, where it is also said that those who take to other processes, namely the processes of philosophical speculation and mystic yoga practice, have much trouble. After many, many years of much trouble, a yogī or wise philosopher may come to Him, but his path is very troublesome, whereas the path of devotional service is easy for everyone. One can achieve the result of wise philosophical speculation simply by discharging devotional service, and unless one reaches the point of understanding the Personality of Godhead by his mental speculation, all his research work is said to be simply a labor of love. The ultimate destination of the wise philosopher is to merge in the impersonal Brahman, but that Brahman is the effulgence of the Supreme Person. The Lord says in Bhagavad-gītā (BG 14.27), brahmaṇo hi pratiṣṭhāham amṛtasyāvyayasya ca: "I am the basis of the impersonal Brahman, which is indestructible and is the supreme bliss." The Lord is the supreme reservoir of all pleasure, including Brahman pleasure; therefore, one who has unflinching faith in the Supreme Personality of Godhead is said to be already realized in impersonal Brahman and Paramātmā.