Three levers,
and no dogma.
Almost every infant sleep problem is a version of one problem: the baby cannot get from awake to asleep without help. It is an ability that develops gradually across the whole first year — and for a sizeable minority, well beyond it. Everything else is detail.
Timing
The most common cause of a bad night is a badly built day. A baby who has been awake too long is not sleepy, they are wired — overtiredness makes falling asleep harder, not easier. A baby who has not been awake long enough has no sleep pressure to fall on.
This is also why short naps and night waking are the same problem wearing two hats, which almost nobody tells you.
Environment
Dark, cool, boring, and consistent. This is the cheapest lever and the one most often half-pulled — a room that is nearly dark is not dark, and at four months that difference starts to matter.
Safe sleep sits here too, and it is not negotiable: on the back, alone, on a firm flat surface, with nothing else in the crib. Every book we publish opens with the same page on this.
Association
Whatever is happening as your baby falls asleep is what they will look for when they surface between sleep cycles. If that is you, they will need you — five, six, seven times a night.
This is the lever people mean when they say “sleep training”, and it is where the arguing happens.
Where we stand on the arguing
We do not pick a side. There is a real spectrum here, from staying in the room and never letting your baby cry, through to graduated approaches with defined intervals. They differ in how fast they work and how hard they are to carry out. They are all defensible, and the honest answer is that the best one is the one you can actually complete.
A method you abandon on night three is worse than a slower method you finish. So No. 01lays out the whole spectrum and helps you choose based on what you can live with — not on what a stranger with a course insists upon.
What we will not say
- That your baby will sleep twelve hours by night three.
- That there is one correct method and the others are cruel or lazy.
- That this is happening because you did something wrong.
- That any of this replaces your pediatrician. Every book ends with the signs that mean you should stop reading and call one.