Nelson’s works create situations in which a person would feel temporarily lost, and this feeling of being lost would lead to a doubt of our senses of perception, and possibly doubt about our ability to perceive an architectural surrounding ‘correctly’. The uncertainty that this instills in a person about the dependability of our mechanisms of perception may not be unique to this feeling of being lost. In artworks by some of Nelson’s contemporaries, the repetition of architectural elements and spaces that Nelson employed towards this feeling of being lost is used towards another kind of uncertainty that could help clarify what the use of this uncertainty might be. Whereas Nelson’s doubling of rooms calls attention to our disorientation and to question the certainty of our perception of the world, Gregor Schneider denies the possibility of knowing what is an addition or recreation and what is original in order to question whether a difference exists and if this difference is perceptible. These two techniques result in a similar destabilization that can evoke a reconsideration of how we relate to surroundings. Like Nelson, Schneider has duplicated identical rooms and environments. Schneider’s doubling operates differently in that it is not being used for making a person feel lost, but nevertheless similarly works at introducing uncertainty and instability into our relationship with the immediate surroundings. Schneider has doubled walls, windows, rooms, houses and their occupants in various projects. In his most famous work, "Totes Haus Ur" (1985-present), rooms were layered so that walls were built in front of walls. In one place, seven windows were built in front of each other.

In this house Schneider has built copies of real rooms, as he states, “many of the works are easy to describe: wall in front of wall, room inside room, ceiling under ceiling. The built rooms are made of walls, a floor, a ceiling, and they are copies of real existing rooms.” This fills the architectural environment with a feeling of uncertainty, a kind of doubt. Though the rooms are ‘real’ – built of proper construction materials and without any sense of being a stage set or even an installation – they are permeated with this uncertainty that is somehow destabilizing of what is ‘real’. In another of his projects, "Die Familie Schneider", two neighbouring row houses in London (2004, Walden Street No. 14 & 16) were made to be entirely identical by building rooms into the existing rooms. There were also people inhabiting the houses, all twins so that they were also identical in each house. Perhaps the culmination of this doubling, at least thus far in his practice, was his work “Neuerburgstrasse 21” (2014, Cologne Germany), in which he repeated the same bathroom twenty-one times in a sequence of interconnected rooms within one large room.

Articulating uncertainty

Glen Seator created doubled architecture some years before Schneider, three projects in particular: “Approach” (1996-97) and “Within the line of the studs” (1997) which replicated the façade of the building in which each installation was built, and “Fifteen Sixty-One” (1999) which replicated an east Los Angeles cheque cashing service into the Gagosian gallery in Beverly Hills. Similarly to Schneider, the method of construction and the materials for the construction have to be identical across the ‘original’ and replication in Seator’s work. This is evidenced in "Approach", where Seator replicated the street, sidewalk, and facade of Capp Street Project within its gallery space. Every detail was replicated, down to the graffiti on the telephone poles and the differences in the aggregate used in the concrete paving. Seator's work offers a kind of stuttering architecture, a replication in such detail as to repeat the material reality of the original.

Rather than an installation towards referencing particular histories, characters, or ideas, the relationship between doubled rooms becomes paramount. In this situation we don’t doubt whether the rooms are doubles, but instead a disorientation develops in that we doubt our perception of the environment. Schneider works to make this difference between doubled spaces imperceptible to the point that there is no original or replica, but rather doppelgängers. Whereas a replica is always referencing its original, the doppelgängers can exist in their own right, as two originals that are identical. Schneider questions whether the relationship between the newly constructed and original rooms can be felt or perceived by a visitor. The relationship might be invisible, as the newly constructed room might completely occlude the original room. He states,

The disappearance of the artwork, that it could be overlooked, does not prevent it from being sensed or for influencing perception. Schneider draws attention to the habit of overlooking, of not sensing what is the difference.
Such duplication creates a sense of tentativeness in interactions with other environments, as doubt creeps into what we think are trustworthy perceptions of environments. Whereas Nelson’s doubling of rooms calls our attention to our (dis)orientation and to question the certainty of our perception of the world, the replication and repetition of Seator and Schneider result in raising questions about our ability to perceive what is real, as well as cast doubt on the idea of a singular original quality in any object we perceive.