While many Jewish anarchists were irreligious or sometimes vehemently anti-religious, there were also a few religious anarchists and pro-anarchist thinkers, who combined contemporary radical ideas with traditional Judaism. Some secular anarchists, such as Abba Gordin and Erich Fromm, also noticed remarkable similarity between anarchism and many Kabbalistic ideas, especially in their Hasidic interpretation. Some Jewish mystical groups were based on anti-authoritarian principles, somewhat similar to the Christian Quakers and Dukhobors. Martin Buber, a deeply religious philosopher, had frequently referred to the Hasidic tradition.