In 1958, Gerald Holtom drew an inverted "V" and crossed it with a line before fitting it inside a circle, creating the peace sign. Nineteen years later, Milton Glaser placed a simplified heart design between the letters "I" and "NY" and created the iconic "I ♥ NY." In so doing, these illustrators added to our visual lexicon. They took what was once the domain of words and sounds, and they drew a visual translation. Thus, just as writers coin words, illustrators coin symbols. This ability ranks as one of the powers of a visual artist.
To create icons or symbols, artists draw never-seen-before combinations of marks or, alternately, they explore the magic of figures of visual communication. Unlike the peace sign, which in itself doesn't look like peace, figures of visual communication allow illustrators to introduce new signs that need little to no explanation, because their appearance usually relies on a combination of existing and recognizable images. And remember, by definition, an illustrator's job is to enlighten, make clearer; therefore, clarity (that is, no need for explanation) drives our efforts.
Imagine an old-style iron key. Now, instead of the typical oval shape for the bow (the part held between your fingers as you turn the key), draw instead the shape of a heart. You now have created a sign to symbolize the key to one's heart.
Figures of visual communication, a phrase adapted from literature's "figures of speech," come to life as the result of many different types of processes or operations, such as the substitution of the oval with the heart onto the key in the example above.
In class, I presented many such families of processes, including one based on arithmetic operations, as a method for creating new signs. Here is a visual summary of it.