What would Marx see as the basis for people's ideas and values?

To Karl Marx, the basic cause of people's ideas and values
is the "base" of their economy.  To Marx, everything about a society other than its
"base" is a "superstructure" that is built on and depends upon that
base.

A society's base is, to Marx, a set of economic
factors.  The base is made up of things like the relationship between the owners of the
means of production and those who do the work.  This relationship, along with things
like the way in which labor is divided up, is what forms the basis of the
culture.

Therefore, people's ideas and values will be
formed by the base and by their position within that set of relationships.  A person who
is from the working class will have different ideas and values, for example, than one
from the class of property owners.