You are not calling a function like that, you just define the function.
The correct approach is to define the function outside document.ready
and call it inside:
// We define the function
function validate(){
console.log('validated!');
}
$(document).ready(function(){
// we call the function
validate();
});
Another option is to self invoke the function like that:
$(document).ready(function(){
// we define and invoke a function
(function(){
console.log('validated!');
})();
});