Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Why Quantum Mechanics is Hard to Understand   To understand the foundations of quantum mechanics, we have to think
carefully about how theoretical concepts are rooted in -- and limited by -- the
nature of experience, as Bohr attempted to show. Geometrical pictures of
physical phenomena are favored because of their clarity. Quantum phenomena,
however, do not permit them. Instead, the historical and dynamical aspects of
description diverge and must be expressed in different but complementary
languages. Objective historical facts are recorded in terms of objects, which
necessarily have an imprecise, empirical quality. Dynamics is based on
quantitative abstraction from recurring patterns. The "quantum of action" is
the discontinuity between these two ways of looking at the physical world.

10
The categories of this paper are: q-bio
37
The categories of this paper are: supr-con
19
The categories of this paper are: eess
8
The categories of this paper are: hep-ex
22
The categories of this paper are: chao-dyn
32
The categories of this paper are: atom-ph
31
The categories of this paper are: ao-sci
14
The categories of this paper are: math-ph
4
The categories of this paper are: cond-mat
36
The categories of this paper are: cmp-lg
2
The categories of this paper are: math
9
The categories of this paper are: nlin
25
The categories of this paper are: patt-sol
15
The categories of this paper are: nucl-ex
28
The categories of this paper are: alg-geom
20
The categories of this paper are: acc-phys