The triangle, square, and circle are central to the philosophy of aikido, and symbolize important aspects of the art. The triangle represents fire and water, and symbolizes various trinities such as mind-body-spirit and past-present-future. The triangle represents the flow of ki and a stable physical posture. The circle is the universal symbol for infinity, eternity, serenity, and perfection. The circle is fluid with no beginning and no end. As you accept and understand the principle of the circle, you will find that it is big enough to apply to your whole life, yet small enough to apply to your aikido techniques. The square is stability, order, and applied control. Together, they represent and symbolize the interrelatedness and harmony of humankind (triangle), earth (square), and heaven (circle).