Dr. Eliezer (Leon) Ehrenpreis was once present at Mesivta Tiferes Jerusalem when a man came to meet Rav Moshe Feinstein ztz”l. Upon first laying eyes on the gadol who was physically slight in stature the man remarked in surprise “Er iz a kleine mentsch!” [He’s a small man!] “No no ” Dr. Ehrenpreis replied shaking his head. “Er is a zeyer groyse mentsch!”

Often another great mind will appreciate aspects of another person’s greatness that others will miss. Everyone revered Rav Moshe for his astonishing erudition and humble personality but few were truly able to appreciate the depth and subtlety of Rav Moshe’s thinking. Such a person was Eliezer Ehrenpreis a world-renowned mathematical genius who became a devoted lifelong follower of Rav Moshe.

Dr. Ehrenpreis who was niftar this past Elul at the age of eighty distinguished himself early in life. By age twenty-three he had earned his doctorate by proving what became known as the Malgrange-Ehrenpreis Theorem. (For the mathematically uninitiated explains Dr. Marvin Knopp of Temple University this was an important foundation of the modern theory of differential equations which in turn which helped form the theoretical underpinning for much of modern technological innovation.)

Ehrenpreis went on to a long and productive career in which he served on an all-star lineup of faculties: NYU’s Courant School of Mathematical Sciences Yeshiva University’s Belfer Graduate School of Science Brandeis University Princeton University Yale Harvard the Institute for Advanced Study in Princeton the Sorbonne Hebrew University Bar-Ilan and Kyoto University in Japan.

Dr. Ehrenpreis had not grown up in a religious home; he was educated in public schools and secular universities. But once he discovered the world of Torah in the mid-1950s it wasn’t long before his scholarly mind and passion for excellence led him to the Torah world’s most scholarly and exalted intellect: Rav Moshe Feinstein with whom he deepened his Torah knowledge so extensively that the rav himself awarded him smichah. Ehrenpreis in turn was able to offer his formidable mathematical and scientific skills to help Rav Moshe clarify many thorny and complex halachic issues.

Dr. Ehrenpreis is unfortunately no longer with us to be able offer his recollections of Rav Moshe. But his wife Ahava a freelance writer and former instructor in Judaic studies at Touro College generously offered to share with Mishpacha her memories of her husband’s relationship with Rav Moshe.

To read the rest of this story please buy this issue of Mishpacha or sign up for a weekly subscription.