Rules help us understand behaviors and actions that are acceptable
(or inacceptable). Even in a sport, where two teams compete against
each other, rules exist to govern the interaction between the teams;
both teams agree to abide by the rules and in that cooperation they
compete to declare a victor. Who would want to play a game of chess
with me if I could ignore the rules of chess, while my opponent was
required to abide by them? Or even worse, what if neither
competitor abided by the rules of chess? In aikido, we use rules to
learn how and why we move and what interaction in and is not
appropriate during training.

The phrase "ai ki" refers to the harmony, the cooperation of
energies towards a uniform goal; a balance to maintain a harmoneous
state. In practice, aikidoka work in cooperation to experience a
balance of harmony to experience and understand the complexities
required to achieve such a delicate balance. Part of training is
learning when you achieve that balance and teaching your body to
replicate that feeling or muscle memory. Aikido training is
learning what is right and wrong. This is why some of our training,
especially in the beginning, is dependent upon "cooperation" from
our partner.

Later in training, we learn that "cooperation" from our partner is
not necessary to practicing aikido. As our partners learn the
dangers and vulnerabilities their body exposes during practice, they
become more sensitive to those dangers and their bodies naturally
move to relieve those vulnerabilities. In this advanced stage of
training, partners can move away from cooperation because they now
move naturally to establish a harmony in their interaction.

Do not confuse cooperation with competition because they are not the
same concept. Do not compete with your partner because the purpose
aikido is not to declare a victor of the competition. Cooperate
with your partner because the purpose of aikido is to understand
harmony.