I cannot help but throw in my two coppers, being one interested in Theurgy myself.
Let us not forget the most widely accepted definition of magick (as postulated by Crowley). Please no flaming here. Even if you do not agree, the eruditious sort who are drawn to this Art and Science are by and large a well-learned bunch, and at least KNOW this axiom.
Magick is the Art and Science of causing Change in conformity with Will.
That's it. End.
Now, it becomes a spiritual thing when one begins to examine what exactly constitute Change and Will. The implications thereof are too numerous to enumerate here.
However, let us not forget that it is also a
science. Much as the science of philosophy has the ability to change those who study it, it is still by and large an intellectual pursuit. In psychology, or philosophy, or any other "soft" science, change is part and parcel of the field. So it is in Magick.
Change is attained in Magick, whether one wants it or not. It is an inevitable effect of the study. Whether or not you attach spiritual meaning to those changes is irrelevant. When one begins working with the energies that permeate the multiverse, an understanding begins to become nascent in that person, and those energies leave that person forever altered. Once you've entered that realm, there is no return.
Those of you who stated that, as with anything one puts effort into, magick leaves an indelible imprint on the individual are so right. The Path of magick, whichever form one walks it in (theurgy or thaumaturgy, in this case), is a difficult one. As with all things that tax an individual's resourcefulness, intellect, stamina and determination-magic too can leave a person forever changed by simple virtue of sustained effort over time.
Before going too much further into this, I would like here to make a distinction as to what I personally consider to be a true magician, as opposed to a simple conjurer of tricks and gimmicks, amusing only to the jester. You see, the idea of magic today is that the magician can unlock doors, call storms, make fire, etc. This is magic, but practicing magic does not truly make one a magician. It is then necessary to consider the actual linguistics of the words magic and magician. You see, magic comes from the word magia, which means literally “wise arts.” The adept of this wise art was called a magus, or “wise man,” from whence we pull the word “magician.” So you must therefor consider if doing the occasional neat trick actually makes one a wise man, or a simple entertainer. I believe it does not. You see there are magicians, and then there are people who can do things that are called magic. There is magic, but then there are gimmicks and feats that, though interesting and entertaining, are not worthy of pertaining to the class of the wise arts.
And so I will offer my distinction between the two right here and now. A jester will call upon the wind to impress those whom he has gathered, and an idler will call upon the wind for no reason other than the fact that he can, but a magician will call upon the wind because he is looking upon a group of sweating workers who have been laboring in the hot sun all the windless day. A jester will turn to those who will listen and say “observe, for in two days a storm shall come,” and a useless idler will call upon a storm simply to see his own power, but a magician will call upon a storm because he looks around and sees that the grass is brown and the trees are dry from drought, yet none shall ever know the storm was called by him. The entertainer will call a crowd around an injured person and heal him only to hear the applaud of the audience, and the idler will cut himself just to heal himself, but the magician will stand at a distance where he will not be noticed, and mend the bones of an unknowing person whom has injured himself, and the magician shall walk away without saying a word. Therefor we can say that the jester users his feats to entertain and gain recognition to extend his ego. The useless idler knows such feats, but does not seek to gain recognition from them, yet only applies them uselessly. The magician then knows how to work such wonders as the others, but does so only to the benefit of others, and humbly rejects the idea of using them to expand his own recognition. In the same way we can class those three types of magic users in an order from the most bastardized to the truest way of applying magic. The jester learns magic only for self betterment, and is therefore the lowliest of the three. The idler does not seek to increase his ego and recognition with his magic, and is therefore above the jester. Yet nor does the idler properly apply such knowledge, and therefor is useless to the world. Finally, above them all is the magician, who uses his knowledge only for the betterment of the world around him, completely devoid of selfishness, and who devotes his entire life to study and sweats blood not for himself, but for the people he crosses on the street everyday, whom will never know his greatness.
The spiritual path of the magician, then, is much like that of any spiritualist seeking a higher truth and a level of spiritual enlightenment. It is one devoid of selfishness and full of self denial. It is in its purest form a path of purity and righteousness, just as beneficial, yet just as difficult, as that of the true Christian, or true Buddhist. And so therefor the path of the magician is similar to any spiritual path seeking higher truth and enlightenment.
The magician is ultimately a servant, and perhaps the lowliest of all servants, to the universe. Indeed a petty slave is the magician, who can only wrought such feats as he is accredited by falling to his knees and begging as a child that something happen. All the while, the request the magician has made, which we call spells, can be examined and rejected. Magicians are beggars that beg for the well being of others in that sense. We pray for their souls where they can not, or help others in ways they can not.