"I don't have time to do nothing"

The efficiency argument is the one that sounds most adult. You're busy. The walk to the car is four minutes and the queue is ten, and those minutes were going to be lost anyway, so the fill turns waste into value. Doing nothing is a luxury for people with more time than you.

Look at the arithmetic. The walk to the car takes four minutes with a podcast on and four minutes without. The queue is ten minutes filled and ten minutes empty. The fill doesn't save any time. It spends the same time on something, and the question is only what that something is. Chapters 5 and 8 are about what the empty version would have been spent on, which is the sorting of the day and the arriving of ideas, and those aren't nothing. They're the work that doesn't get done at a desk because the desk has a screen on it.

There's also what "doing nothing" means. The person on a walk with no podcast isn't doing nothing. They're walking, and noticing the street, and letting the meeting file itself, and having the thought about the email. That's a full four minutes. The person with the podcast is walking and listening, and the listening has taken the slot that the noticing and the filing and the thought were going to use, and they'll need another slot later, and there won't be one, because every slot is filled.

The efficiency argument gets the direction wrong. A day with no quiet in it isn't a day that's used every minute. It's a day in which a whole category of work has had every one of its slots taken by input, and the work has piled up, and the pile is what you're lying awake with. The four minutes to the car were never wasted. They were the only time the day had for the things that need no screen, and the fill is what wastes them.

There's a version of the efficiency argument that's about guilt rather than time. A quiet walk feels like idleness, and idleness feels wrong, and the podcast is a way of not being idle. I'd only say that the person who solves the problem in the shower wasn't idle, and that the guilt is a leftover from a picture of productivity that counts input and not output.

If you genuinely haven't got time to do nothing, that's the strongest reason in this book to leave the walk empty. The busier the day, the more it needs sorting, and the sorting happens in the quiet stretch or it happens at three in the morning, and one of those is four minutes on a pavement.