In his work On The Sublime (Peri Hypsous), Longinus (or often called as pseudo-Longinus because of doubts of authorship) gives 5 sources of sublimity. These five sources are warranted for a work to become sublime. A work is "sublime" means it is extraordinary and great. In other words it has something that makes it inspirational and superior from other artistic creations. Longinus emphasizes the need of highness and elevation in style to give sublimity. Besides being aesthetic, his work is also an important basis of traditional literary criticism, distinct from that given by Plato, Aristotle, etc.
Now let us define these 5 principle sources that provide grandeur to any artistic work:
First and most important is the power of forming great conceptions…(On The Sublime)
Any work finds inception with a thought or an idea. Every work should be produced with high thoughts and grand ideas. It is obvious that with bad and corrupted thoughts or poor ideas, something good and of admirable quality can never be created. So the thoughts and ideas should be sublime to produce a sublime work.
Secondly, there is vehement and inspired passion…(On The Sublime)
Without true passion and emotion, sublimity cannot be achieved. For a work to become sublime, the passions behind it should be intense and should evoke inspiration.
Please note that these above two sources are based on the intuitive capacity of an artist. This cannot be achieved through any formal training. The remaining three I am listing now, however, are a result of artistic prowess.
The due formation of figures deals with two sorts of figures, first those of thought and secondly those of expression…(On The Sublime)
A good artist always decorates his work with good and right figures. The figures of speech should not be superficial decorations however. They should be correctly and carefully used.
Next there is noble diction…(On The Sublime)
For a work to become sublime, it is important to have a grand, noble diction. Diction means choice of words or language used. Now if someone has good ideas, strong emotions, etc. but cannot choose the right words, his work will lack beauty and sublimity, to be very simple.
The fifth cause of elevation — one which is the fitting conclusion of all that have preceded it — is dignified and elevated composition…(On The Sublime)
The last source of sublimity focuses on combining or ordering everything from ideas, emotions, figures and diction together with excellence and perfection such that there is harmony and dignity in the composition.
If a work lacks these things, it is bad or to the very least ordinary.