Is teaching an art or a science?

Professor Daniel Willingham suggests that:

Education is about changing the world, while science is about describing the world.  Daniel concludes that teaching is neither an art nor a science, but mid way between them, as it is about creating something, based on the boundary conditions.  He also uses the house construction metaphor for scaffolding of learning.

Is teaching an art? I reckon yes, as teaching cannot be practised without consideration of the context and people (teacher and learners) involved.  As every one of us is different, what works for one person in teaching and learning may not work for others.  The concept of scaffolding of learning is an art:

Scaffolding is the process by which teachers use particular conceptual, material and linguistic tools and technologies to support student learning. Scaffolding can be used at any point of interaction between teachers and students – at the point of providing inputs and explanations, through to modelling, interacting and assessing.

Is teaching a science? May be teaching could be based on certain scientific principles (mainly psychological principles and behavioral science), but again, these principles are all based on assumptions that education on human’s learning could be objectively assessed, and teaching being assessed in association with learning performance.

To what extent would teaching be based on scientific principles?

Here are some suggested Principles of teaching and Principles of learning from Carnegie Mellon University.  In reflection, most of the principles relating to teaching are based on experience and research, and are context and situations driven.  I reckon some of the adult teaching principles are based on science, with psychology as the basis, whilst others are based on art, especially when it comes to teaching using scaffolding of learning and social interaction, and the mediation of learning through technology.