Earnestness isn’t exactly a hot commodity in today’s art scene, but accompanied by other virtues – pluckiness, generosity, and aspirations for some kind of mystical comprehension – it can still make for potent art. “Fifty Years” shows Robert Neuman bringing these qualities to a lifetime of abstract painting. From an energetic (if well-traveled) Abstract Expressionist style in the 1950s, his work evolved through several kinds of geometric abstraction and even flirted with Surrealism and Op Art. Though the results occasionally seem mannered, a poignant longing for the transcendent runs through these nearly three-dozen works.

Mr. Neuman was born in 1926 in Kellogg, Idaho, then a rough-edged silvermining town. As a youth he loved to draw, but he didn’t glimpse the inside of an art museum until age 20, when he moved to the Bay Area to study art. His timing was right; the Bay Area painting scene, enlivened by the likes of Clyfford Still, Richard Diebenkorn, and David Park, was approaching its peak. Its impact is apparent in the calligraphic gestures and painterly textures of Mr. Neuman’s early canvases. Even his later, more geometric work shows an interest in mystical spaces typical of West Coast artists like Mark Tobey and Sam Francis.

From the start, Mr. Neuman’s themes were inspired by his environment. A Fulbright-sponsored stay in Germany, a country still recovering from the ravages of war, led to the “Black Paintings” series of somber, heavily worked canvases. The stark shapes brushed and scratched into the dark, lumpy surface of “Small Black Painting” (1952) lend it a primordial moodiness.

Mr. Neuman’s palette soon lightened to exhibit a dynamic sense of color. In “Untitled” (c. 1956), ragged strokes of ethereal blue-green, dusky red, and yellows – ranging from earthy shades to elusive tints – electrify a deep space of creamy off-whites.

The “Barcelona” series introduced bold verticals and horizontals that hint, in a canvas like “Plaza Real” (1958), of sun-drenched structures. A certain theme fatigue sets in with “Cinco Vistas de Betran y Serra” (1959); this neat, side-by-side grouping of five vertical panels feels slightly manicured, suggesting the dilemma of any expressionist: How do you keep an art of extremis new once it becomes a school of thought?

The ’60s saw some more deliberative styles, with an emphasis on geometric articulations that harken back to Mr. Neuman’s youthful enthusiasm for drawing. Large, emblematic circles dominate “Pedazos del Mundo” (1962), while the “Space Signs” works are packed with countless, bright circles, and spots endlessly rotating and orbiting one another. With its eye-popping pizzazz, “Space Signs #3” (1968) comes close to an Op Art aesthetic.

A small mixed-media work from this period, “Study for Homage to the Poet” (1970), hums with vital forms and textures. A pale-green square, articulated by irregular white bands, presses a dense red to the image’s top edge, leveraging an oddly faceted rectangle in-between – a figure in a landscape?

The more complicated works in the “Ships to Paradise” series come uncomfortably close to illustration. In these, descriptive tidbits – waves, masts, folksy animals, humans – accumulate in whimsical hordes. Jauntily lettered inscriptions suggest the picturesque surrealism of a record album cover. Such works show the artist’s stubborn independence (and even anticipate the kind of art one sometimes finds today in Chelsea), but gallery-goers may miss the genuine eeriness of Paul Klee’s images, which are animated by offbeat rhythms rather than literalistic allusions.

In the ’80s, Mr. Neuman initiated several new series, some of which he pursues to this day. The “Alhambra” series is particularly handsome; these works on paper insert elegant sets of vertical lines into larger, angular compositions. The 6-foot-wide,heavily encrusted “The Black Rose” (1983) takes an entirely different tack, using only matted textures – no outlines and the barest of coloring – to define a complex form.

The “Lame Deer” series employs cryptic, calligraphic marks to yet another purpose – the evocation of abstracted Native American landscapes. As illustrations, these would amount to mere hopeful roadmaps to the mystical. Luckily, they have the pictorial vigor of painting. The outlines of tepees shift above and below the horizon with rhythmic precision in the small “Lame Deer Bear Paw” (1989); the large canvas “Lame Deer Greasy Grass” (1998) modulates its depths with punchy reds, blue-greens, and yellows.

The installation isn’t strictly chronological, emphasizing the startling variety of work instead of the progression of styles. In a way, this gives the truest accounting of an admirable life in art – of a continuous experimentation with forms and means, with aspirations for the transcendent.

It may be that the artist’s imagination sometimes exceeds his formal ambitions, but this, too, can be taken as a sign of independence. One could even compare Mr. Neuman’s multiplicity of themes and his conflation of illustrative and painterly means to those of Postmodernist star Gerhard Richter. The difference, of course, is Mr. Richter’s dispassionate intent. Whether working in expressionistic, naturalistic, or geometric modes, Mr. Richter avoids the onus of derivativeness by making derivation the whole point; he measures the condition of art rather than the human spirit. Mr. Neuman, by contrast, is a believer: He’s all heart, with the triumphs and shortfalls to match.

Until March 4 (113 E. 90th Street, between Park and Lexington Avenues, 212-987-4997). The gallery declined to disclose its prices.