Infamous magican, Aliester Crowley (1875 – 1947), explained that magick  is the “Science and Art that provokes change in conformity with the Will”, and that “all intentional acts are acts of magic.” Crowley noted that will had the agency to merge with the primordial flow of the universe So, in order to act upon nature all that was needed was to channel that will together with intention.

     His Magus maintains that human beings by nature, have the capacity to produce changes in their environment and that the only requirement to prompt this was to follow one's own path. That is, to do as we wish. In his book Magick in Theory and Practice he explains:

     "Anyone who is forced from his own course, either through  not under-standing himself, or through external opposiition, comes into conflict with the Order of the Universe."

      He goes on to say: "The science of magick is understandinng one's self and one's own situation. It is the art of applying this knowledge in action."

It seems almost as if his definition of magic could have come from a psych-ology manual on the importaince of self-knowledge,

    Prayer could be said to be a magickal process, as might the use of affirmations or any act designed to cause intentional change. To change nothing into some-thing and something into something else.

    The spelling with the terminal "k" was re-popularized in the first half of the 20th century by Aleister Crowley, as a means of indicating the kind of magic which he performed. K is the eleventh letter of several alphabets, and eleven is the principal number of magick, because it is the number attributed to the Qliphoth - the underworld of demonic and chaotic forces that have to be conquered before magick can be performed. K has other magical implications: it corresponds to the power orshaktiaspect of creative energy, for k is the ancient Egyptian khu the magical power. Specifically, it stands for kteis (vagina), the complement to the wand (or phallus) which is used by the magician in certain aspects of the Great Work.

      For Crowley, the alternate spelling was used to differentiate it from other practices, such as stage magic.  Magick is not capable of producing "miracles" or violating the physical laws of the universe (e.g., it cannot cause a solar eclipse), although "it is theoretically possible to cause in any object any change of which that object is capable by nature".

Crowley preferred the spelling magick, defining it as "the science and art of causing change to occur in conformity with the will." By this, he included "mundane" acts of will as well as ritual magic. In Magick in Theory and Practice, Chapter XIV, Crowley says:

What is a Magical Operation? It may be defined as any event in nature which is brought to pass by Will. We must not exclude potato-growing or banking from our definition. Let us take a very simple example of a Magical Act: that of a man blowing his nose.

     Crowley saw magick as the essential method for a person to reach true understanding of the self and to act according to one's True Will, which he saw as the reconciliation "between freewill and destiny." 

     Since the time of Crowley's writing about magick, many different spiritual and occult traditions have adopted the spelling with the terminal -k, but have redefined what it means to some degree. For many modern occultists, it refers strictly to  paranormal magic,  which involves influencing events and physical phenomena by supernatural, mystical, or paranormal means