The techniques of Aikido change constantly; every encounter is unique, and the appropriate response should emerge naturally. Today's techniques will be different tomorrow. Do not get caught up with the form and appearance of a challenge. Aikido has no form - it is the study of the spirit - Morihei Ueshiba
Aikido is not an art to fight with enemies and defeat them. It is a way to lead all human beings to live in harmony with each other as though everyone were one family. The secret of aikido is to make yourself become one with the universe and to go along with its natural movements. One who has attained this secret holds the universe in him/herself and can say, 'I am the universe.' - Morihei Ueshiba
The Art of Peace is medicine for a sick world. There is evil and disorder in the world, because people have forgotten that all things emanate from one source. Return to that source and leave behind all self-centered thoughts, petty desires, and anger. Those who are possessed by nothing possess everything. - Morihei Ueshiba
For context, these are from "The Art of Peace", a book by John Stevens. The quotes are out of context and, according to Chris Li (a professional translator, aikido teacher and aikido history specialist), Stevens took numerous liberties when translating them to project a particular image of Morihei Ueshiba. On that note, the book starts with "
Morihei Ueshiba (1883-1969) was history’s greatest martial artist. He was the founder of Aikido, which can be translated as “The Art of Peace.”
The first phrase gives you an idea of the lens used by Stevens. The second phrase is problematic, as "peace" or "harmony" as intended by the title of the book is not a literal translation of "aiki" (合気), contrarily to what's written. In Japanese, this concept of peace would be expressed as "wa" (和) as in "Wadō-ryū karate" and Stevens distorts the original meaning to fit his ideas.
The book fits within a narrative that the postwar Aikikai started pushing in order to maintain their influence as the world's main aikido organization. Indeed, after WWII, the Yoshinkan (Gozo Shioda's branch of aikido) expanded rapidly and opened a brand new training hall (in Tokyo IIRC), while the Aikikai HQ was in ruins, with war refugees still living on the tatami! The Aikikai could not compete neither in terms of infrastructure nor instructors, so they banked everything on their only competitive advantage: their head was the son of Morihei Ueshiba. They crafted a new vision of aikido revolving around the quasi-religious cult of Ueshiba the "invincible warrior" (the title of Steven's biography of Ueshiba) who gave the world a new martial art, the "art of peace". Quotes that originally referred to the unification of the world under the rule of the Japanese emperor (through military conquest) were reframed as universal messages about peace, non-competitiveness was elevated to a dogma, etc. Interestingly, that vision resonated with many people, I guess even more so in the wake of WWII, then with the Vietnam War and the New Age movement.
As a result, today, there are so many radically different versions of aikido that, as said above, it's too much for anybody to define.