Mondrian was strongly influenced by the work of the Cubists whom he discovered after moving to Paris in 1909. In his geometric paintings Mondrian attempted to shut out all reference to the outside world, in a desire to achieve what he called "universal harmony". It is in his use of contrasting primary colours through both balanced vertical and horizontal forms, that he fulfils this aim. Mondrian's importance lies in his development of "pure" abstraction. He was a founding member of the De Stijl journal of 1917, which helped spread his artistic theories.