Photo Credit: Jodie Maoz

Rabban Gamaliel used to say: appoint for thyself a teacher, avoid doubt, and do not make a habit of tithing by guesswork.

Robust psychological research demonstrates that our ability to estimate accurately is negatively impacted by a variety of factors. For instance, estimations for how fast a car was driving when it crashed were influenced by whether the word used to describe the accident was “smashed” or “hit” (Loftus & Palmer, 1974). Estimations are also influenced by one’s mood. People in a negative mood estimated higher frequency of fatalities from common causes of death than people in a positive mood (Johnson & Tversky, 1983). Later research reported by Daniel Kahneman in his 2011 best-selling book “Thinking Fast and Slow” showed that people’s estimates are biased by a host of subconscious, intuitive, snap-judgements (which he calls System 1 errors).


As one example, a phenomenon titled the anchoring effect shows that people’s estimates are heavily influenced by potentially irrelevant reference points conveyed to them at the time of estimation. In a fascinating study, one group of participants were asked if the highest redwood tree was taller or shorter than 1,200 feet and were then asked to estimate the height of the tallest redwood. The second group was asked if the highest redwood tree was taller or shorter than 180 feet and were also asked to estimate the tallest tree. On average, the first group estimated the tallest height to be 844 feet, while the second group estimated an average of 282 feet. As you can see, the answers were influenced by the arbitrary anchoring number presented at the time of the question. (For those interested, the tallest redwood, named Hyperion, is approximately 380 feet tall, and can be found in California’s Redwood National Park.)

Our poor estimating capacity, with the embedded message on the limitations of overly relying on our own judgements, can help us frame Rabban Gamliel’s message in Avot 1:16; “appoint for yourself a teacher, avoid doubt, and do not make a habit of tithing by guesswork.” Commentators point out that this is the first time we are introduced to a sage in Pirkei Avot and not told that he received the teaching from a previous generation. This may seem ironic given his advice to “appoint for yourself a teacher.” In fact, Leiv Avot sees this as reflective of a transitionary period in the chain of transmission, where greater emphasis was placed on logic and innovation. This led to many more disputes. Consequently, Midrash David argues, this change in approach created the need for individuals to seek out teachers to guide them in what was considered a more convoluted process of halakhic decision making. Without necessarily referencing this historical shift, Rashi suggests that the message is that we should learn specifically through tradition, de-emphasizing our own personal logical analysis.

While we have seen the concept of appointing a teacher before (Avot 1:6), many commentaries differentiate between the two presentations. Rambam suggests that the prior mishna is highlighting the importance of having a teacher to help guide us in the process of learning. Here the emphasis is on having someone to provide a concrete halachic decision. This allows us to “remove yourself from doubt,” by relying on the expert decision-making of a teacher. Rabbeinu Yonah goes so far as to suggest that having a teacher is important even if in theory we know more than the teacher. This can be understood in light of the fact that we all have our own biases and errors in decision making. Having someone to discuss ideas with and defer to is an important value.

This theme extends to the third clause of Rabban Gamliel’s statement, “and do not make a habit of tithing by guesswork.” Tithes need to be exact, and estimating. Because of how subjective and imprecise it is, it was not a viable option. This third clause, according to Rambam, is a continuation of the second. In order to avoid doubt, don’t estimate. Mili DeAvot assumes that it is also connected to the first clause. In order to avoid doubt, we may decide to overestimate the tithes necessary, however, the law is that even overestimating provides a halachic problem, as it disallows the Levi from eating the produce. That is why it is essential to appoint a teacher and not just rely on our own estimates, assumptions, or faulty logic.

However, it is also possible to find a trend in the commentaries supporting more autonomous decision making. This read acknowledges the challenge of System 1 errors, but instead of just looking to others to catch the mistakes, it encourages the individual to overcome these fallacies through engaging in more systematic and critical thinking (what Kahneman calls System 2). Mili DeAvot interprets “make for yourself a teacher” as advice not to secure a teacher, but to become a teacher. By engaging with students, the teacher will be able to better clarify his or her thoughts on the subject, leading to better conclusions. Additionally, picking up on the thread that Rabban Gamliel signals in a new age of decreased tradition, Midrash Shmuel argues that we should make ourselves into our own teachers, meaning we should work harder at our own learning so we can better clarify the ideas. Additionally, Rabbeinu Yonah interprets “do not make a habit of tithing by guesswork” as encouragement to think through arguments in a logical and defensible way. Don’t just guess, estimate, or assume. Do the hard work of thinking through the ideas critically.


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Rabbi Dr. Mordechai Schiffman is an Assistant Professor at Yeshiva University’s Azrieli Graduate School, an instructor at RIETS, and the Straus Center for Torah and Western Thought. He graduated YU with a BA in psychology, an MS in Jewish Education from Azrieli and Rabbinic Ordination from RIETS, before attending St. John’s University for his doctorate in psychology.He learned for two years at Yeshivat Netiv Aryeh. He has been on the rabbinic staff of Kingsway Jewish Center in Brooklyn, NY since 2010 and practices as a licensed psychologist in NY. His book “Psyched for Torah,” his academic and popular articles, as well as many of his lectures are accessible on his website,