Many people underestimate the effect that unifying principles have on the study of biology. Unifying principles are used to provide simplifying assumptions to complex problems which allow them to be effectively tackled by the tools at hand. However, erroneous unifying principles will generate simplifying assumptions that lead towards mischaracterizations of problems which inevitably lead to invalid conclusions. The unifying principles of the current Modern Synthesis of evolution are presently being challenged by the Extended Evolutionary Synthesis. However, the Extended Evolutionary Synthesis has so far failed to provide unifying principles of their own, which has caused many to question whether or not the Extended Evolutionary Synthesis is indeed a unique synthesis of evolutionary biology. Here, the concept of evolutionary teleonomy (Ernst Mayr’s concept of teleonomy applied to evolutionary processes themselves) is identified as a unifying principle of the Extended Evolutionary Synthesis. Additionally, specific examples are provided where modern research has been led astray by the unifying principles of the Modern Synthesis which would have been corrected by applying the Extended Evolutionary Synthesis with the unifying principle of evolutionary teleonomy.