This topic has come up a few times this week. Over at Augoeides, Scott is discussing it in the context of evocations and whether it has a role or not. On another private list it was discussed in the context of spellwork. In my personal life, it became an issue this week at my house within the context of exorcism.
Some magicians do not believe it exists at all and have never witnessed it.
Some have witnessed it and think it is a distraction from real work.
Some have witnessed it and feel it is a sign of accomplishment.
Some would go so far as to say that without it, your magick is failing.
My view falls into both the middle categories.
I have witnessed it, many times in fact. Everything from lights blowing out, to physical objects moving of their own volition. So clearly, while I respect the right of people to doubt what they have not witnessed, for me, the debate over its reality is a non-issue. If you are looking to me to convince you, than you are wasting your time. I could care less about your belief in it or not.
In the last category, folks like Lisiewski claim that unless spirits are shaking shit up in your temple, than you arent really succeeding at an evocation. A comment on the same topic by Golden Dawn Hermetic suggests asking the spirit to move a physical object as a test of the spirits reality.
Now, very often evocations of sub-lunar spirits are accompanied by physical phenomina. In my experience, most angelic evocations are not, with the exception of Enochian "angels", which is a different ball of wax. That said, I do not see the physical phenomina as a good test. . Its a good test that you have the attention of something, but not necessarily the spirit you are looking for. The dead for instance are WAY better at creating physical phenomina than demons are
It it true that you should not just rely upon feelings and sensations, which is why I stress meditation so strongly in my teachings. If you are adept at meditation, you will be able to tell your thoughts from outside thoughts.
I also disagree that every evocation needs to be performed to the extent that physical manifestations are present. Once you have done a few of these and have proven the reality of the evocation, you start working with the spirits in a less formal way. Forcing them into as full a manifestation as possible just to ask for something simple or update a situation that they are working on is like requesting an employee take a cross country flight for in in-person meeting just to tell them something you could have said in a phone call.
In most cases where physical phenomina accompanies an evocation, I usually ask the spirit to knock it off, not move more shit around.
In the context of spellwork, whether it involves particular spirits or not, I tend NOT to view physical manifestations of power as a sign of success. I remember a few years ago doing a ritual with a group of witches to effect a certain event. The ritual was accompanied by several manifestations, from items jumping off altars, to sudden flare ups in the candles. This was all viewed as a sign of accomplishment by most there, but turned out to actually be a sign of misdirected energy. We had a lot of mojo, but not a good path for it to travel along. Its like hooking up a great stereo with crappy speaker wires.
As for being able to move specifric objects with the mind at will, in my youth I spent some time focusing on it. I got decent at directing things already in flux such as objects floating in a pool of water or clouds or other such things. As for heavier physical objects, I moved a quarter about a quarter inch once. I could never manage it again. Maybe I will give it another try, its been about 15 years or so...