If prior art discloses a category that comprises X but does not disclose X itself, can you claim X?

When considering whether one can claim an invention X when prior art discloses a broader category that includes X but does not explicitly disclose X, the aspect of obviousness becomes crucial. The prior art's disclosure of a category that encompasses X indicates that while X is not individually claimed, it may still possess qualities or characteristics that are inherent within that category.

Under patent law, especially with respect to Section 103 of the Patent Act, a claim can be rejected for obviousness if the differences between the claim and the prior art are such that the claimed subject matter as a whole would have been obvious to a person having ordinary skill in the art at the time the invention was made. If the prior art provides a clear lead or suggestion towards X, especially if the category is well-defined with attributes that would point to the potential invention, then claiming X can raise questions about its patentability due to obviousness.

Thus, in this situation, while X may not be anticipated (as it is not expressly mentioned in the prior art), the relationship between the prior art and the characteristics of X may suggest that X is a mere logical extension or variation, leading to potential rejection on the grounds of obviousness.