NOT possible. The only way to understand the spirit of Aikido is to DO...aikido...Aikido is a profoundly embodied spirit...
I would agree that doing Aikido is the best
way of knowing it, but I'm not convinced the only
way to achieve an understanding of it (which exists as a graduated thing) is through doing it. One can gain some understanding through contemplation of familiar concepts. For example I understood aspects of Aikido long before I learned of the proper noun. Part of the reason I began studying it was because it already made sense to me (ie-the basic philosophy fit with my preexisting perceptions). Over time that's only been reinforced as that understanding has deepened through the actual practice (though I still consider myself to be wading in the shallow end of the proverbial pool of understanding).
But, since the spirit of aikido can only be understood through the body, merely trying it acknowledges that something spiritual can only be understood through a physical instrumentality, which denies dualism.
Insofaras experience itself is a physical thing (perception being filtered through the physical brain and senses) I'm not sure this brand of dualism takes all physicality to be bad (thus it's not necessarily a denial of learning by doing), but rather that it tends toward the bad, allowing for the idea that some virtue may be gleaned through the physical...though to be honest I'm not familiar with the original poster's school of thought. My understanding of gnosticism is that it is more of a mystical approach, which demands direct interaction with virtue in order to understand it (as opposed to revelatory practices in which someone tells you what is and is not good).