Step 1: Definition of Syllogism.
A syllogism in logic is a deductive reasoning process where a conclusion is derived from two given premises. When both premises are universal statements (e.g., "All X are Y"), the resultant conclusion is necessarily also a universal statement. This principle is a cornerstone of formal logic.
Step 2: Evaluation of Choices.
- 1. Possibly universal or possibly particular: Incorrect. Universal premises in a valid syllogism necessitate a universal conclusion. - 2. Exclusively a particular proposition: Incorrect. A particular conclusion cannot be logically deduced from two universal premises. - 3. Neither universal nor particular proposition: Incorrect. A valid syllogism's conclusion must be a universal proposition. - 4. Exclusively a universal proposition: Correct. If both premises are universal, the conclusion must logically be universal.
Step 3: Determination. Option 4 is the correct choice: Exclusively a universal proposition.
Final Determination: \[ \boxed{\text{The correct answer is 4. Only universal proposition.}} \]