Two shows up now in Chelsea feature pared-down, hard-edged, abstract paintings that address formal modernist concerns through simple, geometric shapes. But despite these superficial similarities, the works on display reflect the strikingly different temperaments and intentions of two ambitious abstract artists: Thornton Willis and Al Held.

Thornton Willis (b. 1936), showing recent paintings at Elizabeth Harris Gallery, fills his canvases with rectangles parallel or perpendicular to the picture plane and what the artist calls “steps,” thick zigzags that move the eye up and down the composition. These works, with splattered drips, pencil markings, areas of thin, washy paint and zones of whipped-up, heavy strokes, come out of a process where chance and incident are embraced.

In Step Up, Willis moves the eye up through the painting using a heavy orange set of steps. The viewer’s eye settles in the upper-right hand corner of the canvas at a lovely, pale blue rectangle. Around the thick orange steps, brightly colored shapes hover in a field of pink. In Songsinger, Willis paints candy-colored rectangles and the spaces between those rectangles with equal attention. The care the artist puts into placement and proportion is clear. Another winning canvas, Dancers in the Sun, is a fluorescent orange field with floating L-shaped joints of bright lime green. Together these high-chroma colors challenge the retina and combine to express bright, almost blinding daylight.

Though these paintings are occasionally quite large (the biggest canvases here are about seven feet tall) and although his color can be very high-key, these works are not loud. The artist says his pictures develop “intuitively” through his “working process,” which he describes in the exhibit catalog as “a spiritual quest.”

Where Willis embraces nuance and incident, Al Held (1928-2005) is willful, creating enormous, forceful compositions made with harsh, hard color. These are not genteel paintings.

Al Held: Alphabet Painting at Cheim & Read covers a six-year span in the artist’s career where Held used flat geometric shapes, sometimes letters, to make tense compositions. Held eventually moved on to science-fiction-like deep-space designs that rely heavily on perspective (as can be seen in his mural in the subway station at 53rd Street and Lexington Avenue). But at this point in his career, Held, like Willis, was exploring two-dimensional modernist principles.

In the exhibition catalog Robert Storr describes the earliest painting in the show, an imposing twelve by nine-foot work titled Ivan the Terrible, from 1961, where an orange X is “sandwiched” over a black and white T, as a composition that leaves the forms “no room to breathe.” The tension created by the weight of the shapes pushing in on each other is unmistakable. Ivan the Terrible, like all the paintings here, is made with heavy acrylic paint—an even, leathery skin of color that curls at the perimeters of the canvas.

The biggest painting, Circle and Triangle, is twenty-eight feet long and twelve feet tall. Here a huge blue circle on the left is painted with a matte lapis lazuli pigment that glows even as it absorbs light. On the right side of the canvas a triangle made from a wide black line creates two smaller white triangles that activate the corner of the composition.

These two exhibits cover many of the same pictorial ideas. But Willis’ work comes out of a belief that “painting is mystical, even magical,” whereas Held’s paintings, enormous objects influenced by Minimalism’s principle of Gestalt and objecthood, have been willed into existence. Gallery visitors have a chance to see where their allegiance lies.

Thornton Willis: Steps, on view through April 13, 2013, Elizabeth Harris Gallery, 529 West 20th Street, New York, NY, 212-463-9666, www.elizabethharrisgallery.com

Al Held: Alphabet Paintings, on view through April 20, 2013, Cheim & Read, 547 West 25th Street, New York, NY, 212-242-7727, www.cheimread.com

More information about Xico Greenwald’s work can be found at xicogreenwald.com