The Importance of a Fresh Perspective
初心 (shoshin) combines the Japanese kanji for "beginning" and "heart." Though 心 does represent the physical heart - look at the big image closely, it shows the valves of a human heart - it also refers to the figurative heart: the mind, the spirit, etc. From this, we arrive at the usual translation: Beginner's Mind.
A Fresh Outlook
Too often, we human beings are burdened by preconceptions. We do not come to a problem with what the law calls "clean hands"; our minds are polluted by external influences prejudicing us towards particular outcomes. These prejudices may be based on what we consider to be common knowledge, or represent a particular political or social viewpoint.
Regardless, preconceptions are weights upon our minds that must be cast off in order to view something with an open heart. By setting aside what we know, or think we know, we ready ourselves for new knowledge and fresh appreciation.
The beginner starts with a lack of knowledge, an openness to knowledge, and an eagerness to acquire knowledge. A beginner does not know right from left; these things must be learned. However, a beginner possesses boundless energy. By reproducing this spirit within ourselves, we touch upon the passion that drives us to expand our universe to include that which we did not know previously, and perhaps simply missed because we were blinded by old perspectives.
Instead of merely thinking outside the box, Beginner's Mind is emptying the box: clearing the mind of the clutter that interferes with viewing things with the eagerness, hope, and energy of a child.
Clearly, to do this for everything would be to act as though we know nothing, and never knew anything. On the other hand, to clear the mind of preconceived notions for one particular case allows us to approach that case with a clear, focused mind, untainted by the past.
Though this is a concept in Zen, it is also the foundation of the scientific method. To begin an inquiry in earnest, we must isolate a question and strip away prejudice, examining it solely on its own merits. In turn, we propose hypotheses and test them, allowing tangible, measurable evidence to take center stage. From this evidence, we derive conclusions and gradually develop theories to better explain the results.
This said, we must guard against empiricism being mistaken for all existence. The Beginner's Mind is intangible, yet is quite real nonetheless.