Heidegger argues that philosophy is preoccupied with what exists and has forgotten the question of the "ground" of being. We find ourselves "always already" fallen into a world that already existed; but he insists that we have forgotten the basic question of what being itself is. This question defines our central nature. He argues that we are practical agents, caring and concerned about our projects in the world, and allowing it to reveal, or "unconceal" itself to us. He also says that our manipulation of reality is often harmful and hides our true being as essentially limited participants, not masters, of the world which we discover.
Heidegger wrote about these issues in his best-known book, Being and Time (1927), which is considered to be one of the most important philosophical works of the 20th century.
Heidegger claimed that Western philosophy since Plato has misunderstood what it means for something "to be", tending to approach this question in terms of a being, rather than asking about Being itself. In other words, Heidegger believed all investigations of being have historically focused on particular entities and their properties, or have treated Being itself as an entity, or substance, with properties. A more authentic analysis of being would, for Heidegger, investigate "that on the basis of which beings are already understood," or that which underlies all particular entities and allows them to show up as entities in the first place But since philosophers and scientists have overlooked the more basic, pre-theoretical ways of being from which their theories derive, and since they have incorrectly applied those theories universally, they have confused our understanding of being and human existence. To avoid these deep-rooted misconceptions, Heidegger believed philosophical inquiry must be conducted in a new way, through a process of retracing the steps of the history of philosophy.
Heidegger argued that this misunderstanding, beginning with Plato, has left its traces in every stage of Western thought. All that we understand, from the way we speak to our notions of "common sense", is susceptible to error, to fundamental mistakes about the nature of being. These mistakes filter into the terms through which being is articulated in the history of philosophy—such as reality, logic, God, consciousness, and presence.
First off, I'd ask what you think "being" is? I see consistently, people show up here and go on God and how God doesn't exist, no evidence for such, but is this difficulty with understanding what being is a contributing factor to understanding what God is? And as Heidegger suggests we are so preoccupied with what "exists" and forgotten the question of the "ground of being", and as I bolded above the investigations have been focused on entities but a more authentic search would be for what underlies all entities and allows them to show up in the first place...........doesn't that sound more like what a God would be? Yet we make and insist to look for God as an entity, a being, but not the source of being or the ground of being. Is that the mistake we make in any kind of attempt at a discussion about God?