Under Korean patent laws, a patent right is initially vested in an inventor, and the justification of the patent right needs to be reviewed under the consideration of whether the recipient can be qualified as an inventor. This paper reviews three philosophical justifications for patent rights and applies them to artificial-intelligence-generated inventions and concludes that an inventor should be a natural person, and artificial intelligence's inventorship is not justified. First, under Locke's labor theory, every human being has property rights to his own person from birth and can expand his ownership, including patent rights, through his manual or mental labor. Artificial intelligence is a man-made object and does not have any basis for expanding property rights therefrom through labor as it is bereft of any innate rights whatsoever to own itself. Under Hegel's personality theory, a natural person has "the right to direct his will upon any object" and is a bearer of free will, which also can be a basis of the right to a patent. Free will is not merely the act of calculation, it's a reflection of Being itself. Artificial intelligence cannot have such self-purpose and dignity as human beings have and thus cannot be justified as an inventor. Under Bentham's Utilitarian view, it is presumed that an individual responds to incentives, and that this response benefits society. However, artificial intelligence lacks any motivation to devise an invention seeking a monopoly. One might argue that if artificial intelligence's inventorship is denied and no natural persons are qualified as an inventor and no one would be able to reap the benefits arising from the invention generated by artificial intelligence. It might be concerning as this will diminish scientists' motivation to develop the technology and eventually lead to a failure to maximize the utility in society as a whole. However, scientists' efforts should be protected only to the extent appropriate to their contributions. No one should be granted the rights to an invention that he or she has not contributed to. Otherwise, once the artificial intelligence technology reaches AGI (artificial general intelligence) or ASI (artificial superintelligence), only small number of owners would enjoy the limitless fruits of such artificial intelligence. Additionally, once artificial intelligence gains legal status, it can expand its rights boundlessly in society, which would pose a menace to humankind. In these cases, the inventorship of artificial intelligence should be denied under the Utilitarian view as it fails to maximize its utility in society. Accordingly, it is submitted that only natural persons are eligible for an inventor. If artificial intelligence generates an invention with no human contribution, the invention becomes the property of the public. However, if a natural person's contribution is insufficient to satisfy the inventorship requirement, it may be necessary to expand the scope of inventorship to include partial contributions from natural persons. In this regard, the work for hire doctrine under copyright provides a hint on how to enlarge the boundary of inventorship. It is suggested that a natural person employer who defines a problem and plans to find the solution using artificial intelligence, as a creative employee, should be credited as an inventor under the ‘invention for hire’ doctrine even if his contribution to a conception of an invention does not meet the current inventorship requirements.