To the untrained eye of the observer aikido looks like people throwing each other around and it may even appear that the person being thrown is throwing himself, but the practise is to develop a sensitivity to movement through an expansion of your awareness. In aikido, both the attacker and defender practise these principles. The person being thrown must be very aware of the intention of the thrower and defends themselves by the act of taking the fall and either dissipating or avoiding the counter attack. Hence the roles are constantly changing and at no stage can either lose their focus as injury is possible. The thrown person needs to get out of there before being struck, immobilised or broken, which is the same motivation as the person being attacked.
The training depends on sincerity of practise, and clear intention from all participants. There is no time for mental thoughts, or desire to win, gradually the mind quiesces. It is the intention that does the work when we stop trying and the sensitivity that protects each participant. Spontaneous movement is the goal and practise is a constant process of refinement. The internal energy of Ki or Chi may flow if ones focus is well developed.
Through practise we begin to realise how difficult one's mind is to control. Through the study of the Art of Aikido the gross world and subtle world become more apparent and life as we know it is seen from a different perspective. Harmony is the goal. Ultimately attacker and defender or observer and observed become one. Duality becomes unity and the space/time continuum changes -This is true Aikido, all else is just practise. Remove harmony or unity as a core principle in Aikido and the art is diminished to nothing more than speed and strength between opponents. Aikido seeks to take control of an attacker's balance and lead their intention. The application of this strategy is based upon circular and spherical movements.  

©Stephen Seymour