Synthesis is generally to introduce a new and different philosophical approach by combining one philosophical argument with another. Synthesis, which has an important place in the actualization of scientific and intellectual development within the mental activity of man, has been one of the most used methods in the field of philosophy as in many other fields. Many philosophers from Plato to Aristotle, from Porphyryus to Fârâbi have used the method of synthesis to form their philosophical theories and put forward different original philosophical views. Some philosophers, such as Ibn Rushd (Averroes), opposed the activity of synthesis, especially in reconciling Plato and Aristotle's views. Although it is determined as a fact that synthesis is an indispensable element in intellectual activities, the implications of its nature and in which conditions the synthesis should be carried out remain a mystery. In that sense, it is understood that it is a necessity to determine the conditions regarding the accuracy and inaccuracy of the synthesis. This article deals in a theoretical framework with the issues of harmonization among philosophical theories in the context of the nature of synthesis and the reconciliation of Plato and Aristotle's philosophies.