The foundational role of autonomy for brain-computer interfaces.

Invasive brain-computer interfaces (BCIs) pose a challenge for describing human-system interactions because they involve a depth of engagement that is difficult to disentangle. This is particularly problematic when clear authorship of decisions is needed. This presupposes that such devices might also decide autonomously in certain situations. Although the use and implementation of such devices are highly disputed in practical ethics, they seem to offer at least therapeutic benefits for persons with, e.g., Parkinson's disease. That is why it is indispensable to develop a conceptual framework that allows a description of the system's interactions with the human agent. The effects of brain-computer interfaces on patients are assessed empirically in studies and hypothesized on a more speculative level via thought experiments. A model to operationalize dimensions of agency, such as responsibility and privacy, has been proposed. Nevertheless, this model is inchoate if it is not related to autonomy, because it is widely assumed that autonomy is not only a characteristic of the human agent but also of the technological system (at least to a certain degree). Consequently, a more complete model is needed that classifies autonomy at different levels (operational, strategic, and moral). Technological systems can only operate on the first two levels because their behavior is based on dispositions within the scope of alethic modality, whilst human agency is based on deontic structures that are expressed via normative attitudes and statuses that cannot be reduced to alethic modality. This crucial difference can be used to develop methods for evaluating the ethical side of BCIs.