Both/And

Our story begins with the pre-history of modern Jewish philosophy and the radical writings of Benedict Spinoza, who considered the Enlightenment’s challenges to Judaism, and found Judaism wanting. We then meet Moses Mendelssohn, the first traditional Jew to engage with the Enlightenment and mount a sophisticated defense of Judaism.
Further reading:
Moses Mendelssohn, Jerusalem, translated by Allan Arkush (102-139)

Moses Mendelssohn had already acknowledged that Jews in the modern era can make choices about how to practice and believe in Judaism, or whether to keep it at all. A range of choices then emerged in response to this new freedom, including ultra-Orthodoxy, the neo-Orthodoxy of Samson Raphael Hirsch, Reform Judaism, and the emergence of Conservative Judaism with Zacharias Frankel, when he said “yes” to both history and halakhah.
Further reading:
Zachariah Frankel in Mendes-Flohr and Reinharz, The Jew in the Modern World (2nd ed., 1995), 194-197, 178-182.

Once Zacharias Frankel and other historically-minded scholars had affirmed that Judaism has always been changing, a question presented itself: How does Judaism change? Frankel and Solomon Schechter, then a lecturer at Cambridge University, both saw the authority for change as rooted in the Jewish People—but which of the people?
Further reading:
Zachariah Frankel in Mendes-Flohr and Reinharz, The Jew in the Modern World (2nd ed., 1995), 194-197, 178-182
Solomon Schechter, “Historical Judaism,” “Excerpts from Seminary Addresses,” and “The Work of Heaven,” in Waxman, Tradition and Change (89-109, 163-172)

In identifying the aspects of Judaism that he considered compelling for modern American Jews, Mordecai Kaplan focused on the human part of Judaism: community and folkways, rather than commandments and spirituality. In contrast, JTS professor Abraham Joshua Heschel sought to reawaken American Jewry to the power of mystery and the imperative to respond to God’s presence in the world.
Further reading:
Mordecai M. Kaplan, Judaism as a Civilization, (3-15, 173-208, 431-435);
The Meaning of God in Modern Jewish Religion, Chapter 1
Abraham Joshua Heschel, God in Search of Man, 3-4, 167, 184-199

Jewish feminism has been a major influence on Conservative Judaism since the 1970s. Judith Hauptman, professor emerita at JTS, has brought her deep knowledge of rabbinic literature to developing new positions on women’s halakhic obligations. Mara Benjamin is soon to publish a book that uses her own experience of motherhood as a lens on Jewish ethics. A further example of innovating out of a thorough understanding of the tradition comes from Arthur Green, who syntheses Kaplan and Heschel into a naturalist mystical theology.
Further reading
Hauptman: “Women and Prayer: An Attempt to Dispel Some Fallacies,” (JUDAISM, Winter 1993) https://ohelayalah.org/wp-content/uploads/article.pdf
Mara Benjamin, The Obligated Self: Maternal Subjectivity and Jewish Thought (2018)
Arthur Green, “Rethinking Theology,” Radical Judaism, 1-15