"Inside-out" is a self-focused approach, whereas "Outside-in" is an approach focusing on needs from the outside to achieve a goal. The problems the SDGs are trying to solve are complex, and people of various cultures and backgrounds work towards the same goal. Inside-out should not be mistaken by the visioning process of "what you want". It is more about "what you can" in this context. From the inside-out, we will only deepen the issues from our point of view. It is desirable to act from the outside-in perspective, taking into account sustainability needs around us. For example, when thinking about social and environmental problems, we should consider how our business affects society and the environment (inside-out) and what we must do to solve social and environmental problems (outside-in). The inside-out approach leverages our strengths, and the "outside-in" approach creates a vision of making a better world based on social and environmental needs to achieve goals.
Following the SDGs' wedding cake explained previously, I can explain outside-in in this way. This approach considers problems that are outside of us as a starting point. While considering how we can resolve a problem, the gap between a goal and a problem initiates solution building. Because the SDGs are a beyond-forecasted vision on desirable international goals, We cannot bridge the gap between reality and goals without an outside-in approach.