I believe the author was talking about the act of writing the software. Modern type inference means that you can mostly code without needing to write down the

I believe the author was talking about the act of writing the software. Modern type inference means that you can mostly code without needing to write down the types in many cases. This line of code is the same in JavaScript or C#: var instance = new SomeClass(); In function definitions, where you are definitely going to need to provide parameter types it's extremely common to document those types in a docblock in a dynamically typed language. At least I always did. So making the types part of the definition is not a significant difference while writing the code.