This article examines the problem of mind-body interaction in Descartes' philosophy, particularly focusing on the tension between his substance dualism and the causal principle outlined in the Third Meditation. Descartes argued that the mind (res cogitans) and body (res extensa) are distinct substances with different natures, yet he acknowledged their causal interaction. This interactionism has been a source of controversy, as it seems to conflict with the causal principles Descartes himself proposed. The article explores the main objections to this interaction, including general objections to the possibility of interaction between physical and non-physical entities, and specific objections related to the causal hierarchy and containment principles. The article discusses how Descartes responded to these objections, emphasizing that he viewed mind-body interaction as fundamental and irreducible. It also examines the interpretation of Descartes' statements about the containment principle, which suggests that the cause must contain everything in the effect. The article considers whether this principle is compatible with mind-body interaction, given their different natures, and explores various interpretations and reconciliations proposed by scholars. It highlights the distinction between formal and objective reality, suggesting that physical states can contribute to the representational content of mental states without violating the containment principle. The article concludes by noting that Descartes' view of causality, particularly in relation to God as the ultimate cause, provides a framework for understanding how mind and body can interact despite their differences.This article examines the problem of mind-body interaction in Descartes' philosophy, particularly focusing on the tension between his substance dualism and the causal principle outlined in the Third Meditation. Descartes argued that the mind (res cogitans) and body (res extensa) are distinct substances with different natures, yet he acknowledged their causal interaction. This interactionism has been a source of controversy, as it seems to conflict with the causal principles Descartes himself proposed. The article explores the main objections to this interaction, including general objections to the possibility of interaction between physical and non-physical entities, and specific objections related to the causal hierarchy and containment principles. The article discusses how Descartes responded to these objections, emphasizing that he viewed mind-body interaction as fundamental and irreducible. It also examines the interpretation of Descartes' statements about the containment principle, which suggests that the cause must contain everything in the effect. The article considers whether this principle is compatible with mind-body interaction, given their different natures, and explores various interpretations and reconciliations proposed by scholars. It highlights the distinction between formal and objective reality, suggesting that physical states can contribute to the representational content of mental states without violating the containment principle. The article concludes by noting that Descartes' view of causality, particularly in relation to God as the ultimate cause, provides a framework for understanding how mind and body can interact despite their differences.