Being at one with the universe. What is it? What I can say is that Aikido can answer the question so I shall give an Aikido perspective on this statement from my personal experiences.
Many times I have trained in the past with those of other disciplines and probably no different from most always at the back of my mind was 'how would my art deal with what the other was doing?' On testing I came across many failures and many successes but was always interested in what the real difference was between the two.
Basically it all boils down to confidence. Confidence in your own art. Now true confidence isn't a matter of just how you feel at the time but actually is a hard earned condition, level of ability if you like.
At that point you are at one with the universe and that includes being at one with your own 'way' whilst being at one with the 'others' way and thus the other's way becomes of no consequence whilst at the same time being respected.
Graham, while I agree that we should be at one with our own martial way and not allow ourselves to be overcome by anxiety or develop some paralytical inferiority complex; how do other's way becoming of no consequence to us work out in a real conflict? How can we be one with the fact that others have a different way while they're attacking us and using a different set of techniques and skillsets, which we are unfamiliar with? How does Aikido answer this question?