Three.js camera rotation error

Firebug is throwing an error saying that "THREE is not defined" on my var camera and I honestly cannot see why. The error doesn't make any sense to me because as I see it; there is a defined THREE right that on the right hand of the equals sign.

        init();
        animate();

        function init()
        {
            var camera = new THREE.PerspectiveCamera( 75, window.innerWidth / window.innerHeight, 0.1, 1000 );
            camera.position.z = 500;

            var controls = new THREE.TrackballControls( camera );
            controls.addEventListener('change', render);

            var scene = new THREE.Scene();

            var geometry = new THREE.BoxGeometry(100, 100, 100);
            var material = new THREE.MeshBasicMaterial();

            var mesh = new THREE.Mesh( geometry, material );
            scene.add(mesh);

            var renderer = new THREE.WebGLRenderer();
            renderer.setSize(window.innerWidth, window.innerHeight);
            document.body.appendChild( renderer.domElement );
        }

        function animate()
        {
            requestAnimationFrame( animate );
            controls.update();
        }

        function render()
        {
            renderer.render( scene, camera );
        }