Do Babies Need Discipline?

You bet. Not as in punishment, which babies don't understand, but using another definition of the word: "training that corrects, molds, or perfects," according to Merriam-Webster.

You may have noticed your baby increasingly "tests" what he can do and how things work. This is how older babies and toddlers learn about the world around them. It's your job to set some limits on that exploration to keep your baby within the bounds of what is acceptable and safe.
It helps, though, not to overdo it on the rules. One way to decrease the number of limits you'll need to set is to provide fewer opportunities for your baby to get into trouble. Babyproof (and later toddler-proof) your home so that it's a "yes" environment to play in rather than one full of no-nos. If you wind up saying "no" a lot, your baby may become desensitized to it and start to tune it out altogether.

Use simple language when you communicate a rule: "Hot." "Not safe." Let your tone of voice — firm, not frightening — help convey your message.

Whenever possible, make an effort to redirect his attention to something more acceptable. Be prepared for it to take many times for your baby to stop testing a particular limit. Babies learn through repetition and practice. Parents survive this phase through patience.