That depends upon what you mean by true.
I believe that all the religions that were revealed by God through Messengers are true religions, but I do not believe everything that their leaders taught and what their followers now believe is true. I believe that the older religions have been altered by man due to the passage of time and those religions are no longer in their original form. I also believe they are in their winter season.
"All that lives, and this includes the religions, have springtime, a time of maturity, of harvest and wintertime. Then religion becomes barren, a lifeless adherence to the letter uninformed by the spirit, and man’s spiritual life declines. When we look at religious history, we see that God has spoken to men precisely at times when they have reached the nadir of their degradation and cultural decadence. Moses came to Israel when it was languishing under the Pharaoh’s yoke, Christ appeared at a time when the Jewish Faith had lost its power and culture of antiquity was in its death those. Muhammad came to a people who lived in barbaric ignorance at the lowest level of culture and into a world in which the former religions had strayed far away from their origins and nearly lost their identity. The Bab addressed Himself to a people who had irretrievably lost their former grandeur and who found themselves in a state of hopeless decadence. Baha’u’llah came to a humanity which was approaching the most critical phase of its history.
‘Abdu’l-Baha writes: ‘God leaves not His children comfortless, but, when the darkness of winter overshadows them, then again He sends His Messengers, the Prophets, with a renewal of the blessed spring. The Sun of Truth appears again on the horizon of the world shining into the eyes of those who sleep, awaking them to behold the glory of a new dawn. Then again will the tree of humanity blossom and bring forth the fruit of righteousness for the healing of the nations.’ Paris Talks, p. 32.’
Some conclusions can be drawn from this fundamental belief. First, all religions are divine in essence and consequently there are no religions which contradict or exclude each other, but only one indivisible divine religion which is renewed periodically and according to the requirements of the age, in cycles of about a thousand years: ‘Our command was but one word.’ Qur’an 54:51. It is therefore hardly surprising if many of Baha’u’llah’s teachings are to be found in former religions either expressly or in an embryonic form. As ‘Abdu’l-Baha says, the Baha’i Faith is ‘not a new path to immortality.’ quoted from: Principles of the Baha’i Faith. On account of this transcendent oneness of all religions, Baha’u’llah exhorted His people to associate with followers of all religions in a spirit of loving-kindness and to make of religion a cause of harmony and peace, not of discord and strife, of hate and division.
The second conclusion is that we cannot perceive what the essence of religion is and what it has the power to achieve if we examine the traditional great religions in their present form. They have achieved much but have reached the end of their road; they were the foundation of great cultures and for thousands of years they were the guiding-star of millions of people in their everyday life and activities. But during the course of history they have also accumulated large amounts of historical ballast. They have moved a long way from their origin and are burdened with their followers’ misdeeds and cravings for power. They are no pleasant sight today, least of all to young people, who no longer see in these religions the ‘salt of the earth’ as Jesus called his disciples, Matthew 5:13 but rather the ‘opium of the people’ (Karl Marx). And one is easily inclined to pass judgment on religion as a whole, and to see in it an anachronism of past times, long since overcome, like the belief in demons in former times. But a withered plant does not give us the faintest idea of its blossoming time. In reality, religions are the ‘light of the world’ and, according to Baha’u’llah’s teachings, the foundation of human culture. It is important to understand that they are as necessary for mankind as sunlight for the plant. Without divine revelation, there would be neither progress nor culture: ‘Were this revelation to be withdrawn, all would perish.’ Taken from (Baha’u’llah, Gleanings, XCIII)."
(Udo Schaefer, The Light Shineth in Darkness, pp. 24-26)
