Dr. Jekyll and Mr. Hyde look differently, so they must be different people. More specifically, Dr. Jekyll and Mr. Hyde have markedly different physical characteristics. Dr. Jekyll is described as middle-aged, distinguished-looking, and a large man. Mr. Hyde is younger, more energetic, and described by just about everyone as seeming to have a deformity. No one can pinpoint exactly what this deformity is, but they unanimously agree that it’s there, and that it’s definitely evil.
Mr. Enfield remarks that "the more it looks like Queer Street, the less I ask." He’s talking about odd phenomena. While Mr. Enfield looks at a mystery and says, "oh, that’s strange," his friend Mr. Utterson looks at a mystery, says, "oh, that’s strange – I wonder what’s going on." Indeed, this is their main point of differentiation.
Dr. Lanyon and Dr. Jekyll have different approaches to science – therefore, they’re different men. Lanyon says something like "I believe in logic and science and rules" and Jekyll replies "I’m going to mess with science until it approaches a weird and supernatural form of abuse."
Stevenson isn’t one for subtlety. He gives us details on the characters without romance or innuendo. For example, his very first paragraph is an extremely lengthy description of Mr. Utterson – "cold, scanty, and embarrassed in discourse…yet somehow lovable."
Remember that paragraph early in the book where Stevenson details Mr. Utterson’s usual nighttime ritual? That whole description can be summed up like so: Mr. Utterson is a boring man of routine.
When speaking to Mr. Utterson, both Mr. Guest and Poole frequently use the term "sir." Poole refers to Dr. Jekyll as "my master." This is obviously not a classless society. Servants are present to be loyal and helpful, but they always defer to the gentlemen. Once again, Dr. Jekyll and Mr. Hyde becomes a portrait of its times.