Art is a complex and powerful tool. When judging it, you have to be careful. It takes quite a bit of specialized knowledge to make a really effective judgment about art. The goal of this section is to just discuss the criteria for judgment. The actual details of such a judgment are more of a science, with all the benefits of specialized knowledge and technical mastery. We want to stick to the philosophical elements, and not pretend to be experts.
The first way to judge art is by looking at the purpose it fulfills. If the art is supposed to embody some kind of worldview, the first question one could ask is what kind of worldview does it convey. The world presented, with all of the metaphysical value-judgments, can be judged on whether it present a positive view of the world, or a negative one. Is it life-affirming art, or life-negating? Are the value-judgments presented factually correct?
If a piece of art shows a world where people live in misery, and human happiness is impossible, the art can be judged based on the validity of those themes. Not only is it factually incorrect, but presents a view of the world that, if believed, would negate our lives. If the art presented a world where fate controls everyone, and people are helpless against it, it is promoting determinism. The result is that people don't bother with the process of living because they think they'll fail or that theirs no point.
So the worldview presented can be evaluated. Is it worse then the real world? Does it negate human values? Or does it emphasize human values? Does it show that success and happiness are possible? And even if it does, what kind of values does it present? What view of happiness is seen as possible? A worldview could be presented that a shallow, mindless, hedonistic kind of happiness is the goal in life. Clearly we can judge that.
A different way of judging art is to look at how effective it is at presenting a re-creation of reality. If the view of the world is clear and well integrated, it more powerfully brings the abstraction to the concrete level. If it's contradictory or poorly selected, the abstraction remains abstract. In other words, does it actually fulfill it's purpose of concretizing an abstraction?
There are many factors that can help you make such a judgment. One could focus on the artistic medium, and whether it effectively conveys the idea. One could focus on the style, and whether it adds to the effectiveness, or subtracts. One could focus on technique and mastery. Each element can add or subtract from the re-creation of reality.
For instance, how could one present a view that life is full of turmoil and hardships when you use cartoon characters in your painting. How can you present a view of beauty and breathtaking passion when your technique is so poor that it comes off an ugly parody.
One can also look at the subject matter itself, and whether it's really compatible with the metaphysical value-judgments being presented. Or one could look at the level of integration of the piece.
Rand discussed how one could recognize a piece of art as being great, while disagreeing with the message it conveys or the world it portrays. You can recognize that a piece is very well done, great integration, perfect selection, and masterful technique, and disagree completely with it. The two are different standards.
Finally, one could judge it by your own personal reaction to it. You can say "I love this". You should be clear that this is a different kind of judgment from the other two. Your own emotional reaction can be partly based on a Sense of Life reaction to the art. It can also be based on an emotional reaction spurred by some other trigger, like enjoying a painting because you had a dog that looks just like the one on the canvas.
Keep in mind that these three kind of judgments are different, although not necessarily independent. A very well done piece of art, strongly conveying metaphysical value-judgments, is more likely to create a strong Sense of Life reaction in a person. The metaphysical value-judgments conveyed will factor into what kind of reaction will take place. But it's not necessary. A great piece of art may have little affect on you, whereas you may respond emotionally to something that's not technically proficient.