You've probably heard of limiting yourself to three sentences or statements for the summary of your presentation. But why three?
Two ideas and the audience is hungry for more. Four or five ideas and it seems that the speaker is starting on a new presentation and testing the patience of the audience. Most of the stories we know from a very young age are elaborated around the number three.
The three wise men, the three little pigs and the three musketeers (they were four). In the English-speaking culture, Three Blind Mice or Goldilocks and the Three Bears. Think of a trilogy, a triptych, and the Holy Trinity. Is the preference for the number three part of our European cultural baggage? Not necessarily, as an example: Brahma-Vishnu-Shiva in Hinduism. Other examples of the symbolism of the number three are present in Buddhism, Judaism, and Islam.
Science gives us some clues as to the importance of the number three if only by the hours spent on school benches solving rules of three and calculating the hypotenuse of a right triangle. One can think of the Buckminster Fuller geodesic dome, designed from equilateral triangles, of which the American pavilion at the 1967 Montreal International Exhibition is a fine example. A resistant structure, even to a fire, for its weight. We will also mention a tripod that, although it is designed of few materials, can support a significant weight with stability: think of the Christmas tree in the family room.
It is by examining the number three throughout the history of philosophical thought that it takes on its full meaning. We can go back to the thought of pre-Socratic philosophers to follow the use of dialectics in the search for truth, opposing rhetoric more interested in oratorical discourse and its form. The dialectic is divided into three statements: the thesis, the antithesis, and the synthesis; or a statement, its contradiction, and the overcoming of this contradiction. For a long time, dialectic has been a form of reasoning that leads to a higher state such as a definition or a truth, but above all, for those who, like us, must convince audiences, it is a powerful tool to advance thought and rally people to our way of thinking.