public function add_rule($field, $rule) {

		if(!$rule instanceof \HybridLogic\Validation\Rule) return $this;

		if(!isset($this->labels[$field])) {
			$this->set_label($field, $this->humanize_field_name($field));
		}

		if(!isset($this->rules[$field])) $this->rules[$field] = array();
		$this->rules[$field][] = $rule;

		return $this;

	}