Is it possible to be a good person and not be a member of the Baha'i Faith?
Why be good?
By divine command. Bahá'u'lláh says:
... Live ye one with another, O people, in radiance and joy. By My life! All that are on earth shall pass away, while good deeds alone shall endure; to the truth of My words God doth Himself bear witness....
Other reasons include:
Universal Eschatology: Because God knows what is good for His people and He only wants them to be happy, content and to live a life in peace.
Individual Eschatology: Because everyone's station after death will depend on one's goodness in this world (and of course God's acceptance
Purely for Love for God (Ultimate and most selfless reason).
'Abdu'l-Bahá, Bahá'u'lláh's appointed Successor and authorized Interpreter of His words, says:
... And the honor and distinction of the individual consist in this, that he among all the world's multitudes should become a source of social good. Is any larger bounty conceivable than this, that an individual, looking within himself, should find that by the confirming grace of God he has become the cause of peace and well-being, of happiness and advantage to his fellow men? No, by the one true God, there is no greater bliss, no more complete delight. Secret of Divine Civilization, pp. 2-3
Is it possible to be a good person and not be a member of the Baha'i Faith?
Yes, especially if one is a member of another of God's religions, which the Bahá'í Faith regard as all authentic; "The holy Manifestations Who have been the Sources or Founders of the various religious systems were united and agreed in purpose and teaching" ('Abdu'l-Bahá, The Promulgation of Universal Peace)
Abdu'l-Bahá even encouraged people to become "true Christians":
Thou didst begin thy letter with a blessed phrase, saying: 'I am a Christian.' O would that all were truly Christian! It is easy to be a Christian on the tongue, but hard to be a true one. Today some five hundred million souls are Christian, but the real Christian is very rare: he is that soul from whose comely face there shineth the splendour of Christ, and who showeth forth the perfections of the Kingdom; this is a matter of great moment, for to be a Christian is to embody every excellence there is. I hope that thou, too, shalt become a true Christian.
While one can be good without being a Bahá'í, there is a great advantage to recognizing the truth of Bahá'u'lláh's Teachings. For example, say there existed a book series, and the first book in the series with all of its sequels contained the answers to all of the questions you could ever have. Now say you find one of these books. It could be one of these books that was already owned by a family member or one you came across unexpectedly. You read the book and realize what a treasure it is. You might even seek out and read some of the earlier books in this series because this one is so exciting and you hope for more sequels as well. But either because you don't know that there exists another sequel in this wonderful series of books or because you have been convinced by others that this book which you read is the last book of the series, you don't even look for any other sequels.
Now, since each sequel in the series summarizes or restates the answers found in all of the previous books, not going back to read any of the previous books in the series may not hurt you; although you would miss out on the beauty and excitement of these books by not reading them. However, since each book contains more of these answers than any of the ones previously written, not reading these sequels means that there are answers on which you are missing out.
The Revelation of God is like that series of books. As humanity matured as a race, a greater measure of God's Revelation was revealed through each succeeding Manifestation. To reveal too much too early would be to give the people more than they could handle. Therefore the Revelation of God's Will and mysteries was revealed slowly and progressively according to the capacity of the people of the time to receive it. Bahá'u'lláh's Revelation contains the fullest measure of God's Revelation thus far given to humanity. Therefore, to miss out on Bahá'u'lláh's Teachings is to keep yourself from knowing as much as you can about the mysteries of God, God's Will for humanity, and the solutions for the world's problems--solutions given by God Himself through Bahá'u'lláh. In addition, Bahá'u'lláh has clearly written that He is not the last of God's Manifestations/Messengers either. So, in a few centuries we can expect another sequel to the Books of the Revelation of God.
Ultimately, though only God can decide who is "good" and who is not. Until we face Him nobody can say for sure if He accepts our acts, even if we think they are good and even if they are in accordance with Bahá'í law.
