One of the fundamental problems when we are trying to interpret the Tractatus is to understand unfamiliar concepts that are hardly found in the tradition of analytic philosophy. For instance, when Wittgenstein claims that ‘logic and ethics are transcendental’, what is the meaning of ‘transcendental’ and how could it be consistently applied to logic and ethics? We claim that these questions should be discussed in the tradition of Transcendental- Philosophy originated from Kant. And the understanding of the concepts obtained from this tradition plays important roles in the following respect: On the one hand, the understanding is directly related to the whole system of the Tractatus. On the other hand, it becomes a cornerstone in understanding early Wittgenstein’s views on ethics. Therefore, we would like to outline the Kantian approach as a framework that could shed light on these problems and to clarify that the goal of the Tractatus has an inseparable relation to something ethical. Subsequently, we will critically analyze the conventional understanding of the concept of ‘transcendental’. In particular, contrary to the Erik Stenius’s interpretation, who understands the meaning of ‘transcendental’ differently, when it is applied to ethics and logic, respectively, in the Tractatus, we will equally interpret ‘transcendental’ as a priori conditions of the world. Finally, we will suggest that early Wittgenstein’s views on ethics are unique, and are related to a problem of the solipsism, which is, a condition of the world.