I'm presently working my way through the 1986 book Aikido and the Harmony of Nature, by Mistugi Saotome. Now, I'm not an ASU (Aikido Schools of Ueshiba) student, but I've been kinda a fan for some years. In videos I've seen of him, Saotome shihan's technique is clean and effortless-looking, and his students are knowledgeable in their approach and powerful in their technique.
Mistugi Saotome was a personal student of the Founder, of the post-war generation, having started at the Hombu Dojo in 1955. He became an uchideshi in 1958 and began teaching his own classes at the Hombu in 1960. In 1975, after meditating on O Sensei's spirit for three days and nights, he moved to the United States and established the ASU in Washington, D.C.. Today, he's retired to Florida, but still teaches the occasional seminar. The ASU has over a hundred dojo in the United States, and several thousand students.
Of all the books I've read lately on the subject of aikido, Aikido and the Harmony of Nature is the most spiritually oriented, and the most new-age-ish. Saotome talks a lot about the Universal Life Force and how it is Love, and Love is God, and God is Universal, and Love is Universal, and how Universal Love is Harmony, Harmony is God, God is in Harmony with Universal Love, and so on. Whole chapters go on like this.
But there is a center, or rather a "centeredness" to his message, which is that the Kami, the Shinto gods to whom O Sensei prayed when he knelt before his shrine and clapped his hands, aren't necessarily different from the Christian, Jewish or Muslim God. And while he does mention that Shinto played a formative role in the development of aikido, he attributes this to the simple fact that the Founder was Japanese.
The basic point he's making is that the source and focus of Western spiritual philosophy and that of Eastern spiritual philosophy are the same, only called by different names. So aikido would look different if it'd been developed by an Irishman, for example, or a German or a Russian, but those differences would be largely superficial. The spiritual source - and thus the basis for the physical movement of aikido - remains the same.
I don't know how far I'd follow that premise. I tend to think of the different religions as having evolved from mostly different sources altogether - sources which have more to do with the worshipper than the worshippee, more to do with the devotee than with the god or philosophy itself. I don't know, of course, and I'm not going to know by the time I finish this book. It is an interesting idea, but one for another day. For right now, it's all I can do to put my feet in the right place, keep my balance and try to move my body in the right way, to effectively use my center to properly control my uke. Whether that center is governed by a god or a set of gods - or by God - is a question that will have to wait for an answer.