I wrote only a short note before about my personal experience. I wanted to leave my answer out of it. But I do have an answer. I believe that the Rambam's rational approach to Judaism holds the key. In the way of thinking of the Rambam's [Maimonides] Reason (i.e. Aristotle's Logic and Metaphysics) and Torah are one organic whole. I think where Judaism (Yidishkeit) went wrong was when this Rambam approach was rejected. (One example of the way of thought of the Rambam is the parable of the King in the Guide for the Perplexed.) In this parable there is a king with a country. People outside the country are barbarians. People in the country are goyim with civilization. People near the palace of the king are Talmudic scholars that know and keep the whole Torah. People in palace are natural scientists. People with the King (God) are the philosophers and prophets.
You can see this approach also in Saadia Geon and the Chovot Levavot [a medieval book on ethics, Duties of the Heart].
This rational approach to Torah was wide spread during the Middle Ages. I think after the time of the Rambam,Yidishkeit deteriorated into fanaticism.
The "Middle Ages" were the age of reason. You almost can never punch a hole in an argument of a medieval philosopher whether Anselm or Maimonides or Aquinas. The characteristic of the great Mediaeval thinkers was that every counter argument against them can usually shows the shallow thinking of the one trying to find the hole. Later thinkers never approach that degree of rigorous thought--ever-- even Kant.
The greatness of the Renaissance was in art and in the beginning of empirical thought-not reason
