In the following question, select the one word which is the best substitute for the given phrase: A perception without objective reality.

Introduction / Context:
This one word substitution question comes from the field of psychology, but the terms are common in general English as well. The phrase a perception without objective reality describes seeing, hearing or feeling something that is not actually present in the external world. You must pick the technical term that fits this description most precisely.

Given Data / Assumptions:
Phrase: A perception without objective reality.
Options: Cynicism, Hallucination, Illusion, Optimism.
We assume objective reality means something really existing in the outside world, not just in the mind.
The correct term is widely used in psychology, medicine and even everyday speech when discussing mental states.

Concept / Approach:
A hallucination is a sensory perception in the absence of an external stimulus: that is, the person sees, hears, feels, smells or tastes something that is not actually there. An illusion, by contrast, is a misperception or distorted perception of a real external stimulus, such as seeing a stick in water as bent. Since the phrase emphasises perception without objective reality, hallucination is the more accurate term. Cynicism and optimism refer to attitudes, not sensory perceptions, and are therefore not suitable.

Step-by-Step Solution:
Step 1: Focus on the key idea: perception without objective reality. This means the mind experiences something, but there is no real external object causing that experience. Step 2: Examine Hallucination. This is exactly defined as a false sensory perception occurring in the absence of external reality, such as hearing voices when nobody is speaking. Step 3: Examine Illusion. An illusion is a misinterpretation of a real external stimulus; something exists out there, but the brain misjudges it. This does not match the absence of objective reality. Step 4: Examine Cynicism. Cynicism is an attitude of distrust or negativity about people's motives; it has nothing to do with sensory perception. Step 5: Examine Optimism. Optimism is a hopeful or positive attitude about the future, also unrelated to seeing or hearing nonexistent things. Step 6: Therefore, Hallucination is the best one word substitute for the given phrase.

Verification / Alternative check:
Compare two brief definitions: Hallucination is perception without object; illusion is misperception of a real object. The phrase in the question explicitly uses without objective reality, which aligns with the first definition. If the phrase had been mistaken perception of a real object, illusion would have been closer. This direct comparison confirms that hallucination fits the phrase most accurately.

Why Other Options Are Wrong:
Cynicism describes a negative attitude about people's sincerity or motives, not a sensory error or mental image without reality.
Illusion involves an external object being perceived incorrectly; since the question stresses the absence of objective reality, illusion does not match fully, even though it is related to perception.
Optimism refers to a hopeful outlook or positive expectation and is unrelated to whether perceptions match reality.

Common Pitfalls:
Because illusion and hallucination both deal with incorrect perceptions, test takers often confuse them. The key difference is the presence or absence of an external stimulus. Remember this: in hallucination, there is no real object; in illusion, there is an object but the brain misreads it. Many exam questions intentionally use phrases like without objective reality to push you towards hallucination rather than illusion.

Final Answer:
The correct one word substitute is Hallucination (option B).