In The Order of Things, published in 1966, Foucault begins with a lengthy discussion of Las Meninas, a painting by the Spanish painter Diego Velazquez. In Las Meninas, Velazquez uses the light to play with complex gazes by concealing the most important subject of the painting. In his analysis of the painting, Foucault develops his central argument. For him, all periods of history have some fundamental conditions to define what is acceptable as truth in scientific discourses. While some discourses have been considered truthful and valid, others can be taken as witchcraft, magic or heresy. Foucault argues that these conditions of discourse change over time through general and relative changes in the episteme from one period to another. In his analysis of Las Meninas, Foucault is interested in finding in another way of looking. For him, the painting represents conflicting viewpoints, multiple foci, on the relationship between art and reality that involves our own gaze as we put ourselves into the abyss. The presence of the painter in his object of art as well as the looking glass with the reflection of the couple makes the observer think about what is central and what is at the margins for the painter. For Foucault, Velazquez reverses the subject/object positions, destabilizing the subject which loses his fixity. By deconstructing the subject, Foucault questions the very idea of truth, essential to the foundation of sciences.